Accessory device, imaging device, control method, storage medium, and lens device

Abstract

To smoothly and quickly communicate large amounts of data between an imaging device and an accessory device. [Solution] The accessory device 100 is provided with a notification channel used for notification from the imaging device to the accessory device, a first data communication channel used for transmitting accessory data from the accessory device to the imaging device, and a second data communication channel used for transmitting camera data from the imaging device to the accessory device. When an accessory control means 111 has received a transmission request as notification from the imaging device, it transmits the accessory data frame by frame, and receives the camera data transmitted by the imaging device in response to receiving the accessory data frame by frame. While transmitting the accessory data while receiving a transmission request from the imaging device, the accessory control means stops transmitting the accessory data in response to a transition from the state where the transmission request is received to a state where the transmission request is no longer received.

Description

[Technical field]

[0001] The present invention relates to an imaging device (hereinafter referred to as a camera body) and an accessory device such as an interchangeable lens, which are capable of communicating with each other. [Background technology]

[0002] In an accessory-exchangeable camera system including a camera body to which an accessory device can be detached, communication is performed so that the camera body can control the accessory device and the accessory device can provide the camera body with data necessary for its control and imaging. In particular, when capturing video for recording or video for live view display using an interchangeable lens, smooth lens control is required in accordance with the imaging cycle, so it is necessary to synchronize the imaging timing of the camera body with the control timing of the interchangeable lens. Therefore, the camera body needs to complete the reception of data from the interchangeable lens and the transmission of various commands, requests, etc. to the interchangeable lens within the imaging cycle. However, as the amount of data the camera body receives from the interchangeable lens increases and the imaging cycle shortens (higher frame rate), communication of a large amount of data is required in a shorter time.

[0003] Patent Document 1 discloses a camera system having a one-way communication mode (hereinafter also referred to as high-speed mode) and a two-way communication mode (hereinafter also referred to as low-speed mode). In the high-speed mode, burst communication is performed to transfer a large amount of data by full-duplex communication using in parallel a one-way communication channel for data communication from the camera body to the interchangeable lens and another one-way communication channel for data communication from the interchangeable lens to the camera body. On the other hand, in the low-speed mode, a request communication from one of the camera body and the interchangeable lens to the other and corresponding data communication from the other to the one are performed using one communication channel while switching the communication direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-237514 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the camera system disclosed in Patent Document 1, when it becomes difficult to perform continuous data communication in high-speed mode due to insufficient processing speed of the microcomputer mounted on the interchangeable lens or the camera body, the data communication cannot be temporarily stopped. As a result, there is a risk of data communication failure. In order to avoid data communication failure, it is necessary to set a low data communication speed as a communication standard that has a sufficient margin for the performance of various expected microcomputers, or to reduce the amount of data to be communicated. However, in this case, even if both the camera body and the interchangeable lens are equipped with microcomputers with high processing performance, the processing performance cannot be utilized, and high-speed data communication cannot be realized.

[0006] Furthermore, for example, if the capacity of a buffer provided in the camera body for storing data transmitted from an interchangeable lens is insufficient for the large amount of data transmitted from the interchangeable lens to the camera body all at once via burst communication, it may not be possible to store all of the data in the buffer.

[0007] The present invention provides an accessory device, an imaging device, and the like that are capable of communicating large amounts of data smoothly and at high speed. [Means for solving the problem]

[0008] An accessory device according to one aspect of the present invention is an accessory device that is removably attached to an imaging device, and includes accessory control means for controlling communication between the accessory device and the imaging device, and in response to a change in a signal level of a first channel connected via a first terminal from a first signal level to a second signal level, the accessory control means performs the following steps in response to the signal level of the first channel being maintained at the second signal level: Without a clock signalThe communication with the imaging device is performed via a second channel connected via a second terminal and a third channel connected via a third terminal. It is characterized by:

[0009] According to another aspect of the present invention, there is provided an imaging device to which an accessory device is removably attached, the imaging device having a camera control means for controlling communication between the imaging device and the accessory device, the camera control means controlling a communication between the imaging device and the accessory device, the camera control means controlling a communication between the imaging device and the accessory device in response to a change in a signal level of a first channel connected via a first terminal from a first signal level to a second signal level, the signal level of the first channel being maintained at the second signal level, Without a clock signal The communication with the accessory device is performed via a second channel connected via a second terminal and a third channel connected via a third terminal.

[0011] Further, a control method for an accessory device according to another aspect of the present invention is a control method for controlling communication between an accessory device that is removably attached to an imaging device and the imaging device, the control method including the steps of: after a signal level of a first channel connected via a first terminal changes from a first signal level to a second signal level, the signal level of the first channel is maintained at the second signal level; Without a clock signal The method further comprises a step of performing the communication with the imaging device via a second channel connected via a second terminal and a third channel connected via a third terminal.

[0012] Furthermore, a control method for an imaging device according to another aspect of the present invention is a control method for controlling communication between an imaging device to which an accessory device is removably attached, the control method including the steps of: after a signal level of a first channel connected via a first terminal changes from a first signal level to a second signal level, the signal level of the first channel is maintained at the second signal level; Without a clock signalThe method further comprises a step of performing the communication with the accessory device via a second channel connected via a second terminal and a third channel connected via a third terminal.

[0013] According to another aspect of the present invention, there is provided a storage medium storing a program for causing a computer to execute a control method for controlling communication between an accessory device removably attached to an imaging device and the imaging device, the control method including the steps of: after a signal level of a first channel connected via a first terminal changes from a first signal level to a second signal level, the signal level of the first channel is maintained at the second signal level; Without a clock signal The method further comprises a step of performing the communication with the imaging device via a second channel connected via a second terminal and a third channel connected via a third terminal.

[0014] According to another aspect of the present invention, there is provided a storage medium storing a program for causing a computer to execute a control method for controlling communication between an imaging device to which an accessory device is removably attached and the accessory device, the control method including the steps of: after a signal level of a first channel connected via a first terminal changes from a first signal level to a second signal level, in response to the signal level of the first channel being maintained at the second signal level, Without a clock signal The method further comprises a step of performing the communication with the accessory device via a second channel connected via a second terminal and a third channel connected via a third terminal.

[0015] Further, a lens device according to one aspect of the present invention is a lens device that is removably attached to an imaging device, and includes accessory control means for controlling communication between the lens device and the imaging device, wherein, after a signal level of a first channel has changed from a first signal level to a second signal level, the accessory control means performs the following in response to the signal level of the first channel being maintained at the second signal level: Without a clock signal The communication with the imaging device is performed via a second channel and a third channel. Effect of the Invention

[0018] According to the present invention ,a A large amount of data can be communicated smoothly and at high speed between the accessory device and the imaging device. [Brief description of the drawings]

[0019] [Figure 1] 1 is a block diagram showing a configuration of a camera system according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a block diagram showing a communication circuit in a first communication setting in the first embodiment. [Diagram 3] 1 is a block diagram showing the configuration of a camera and a lens data transmitting / receiving unit in a first communication setting in the embodiment 1. FIG 2 is a block diagram showing the configuration of a communication unit in a first communication setting in the embodiment 1. FIG 3 is a block diagram showing the configuration of a communication unit in a first communication setting in the embodiment 1. [Figure 4] 5A to 5C are diagrams showing waveforms of signals exchanged between the camera body and the interchangeable lens in the first communication setting in the first embodiment. [Diagram 5] 6 is a diagram showing waveforms of signals exchanged between the camera body and the interchangeable lens in a non-BUSY additional mode of the first communication setting in the first embodiment. FIG. [Figure 6] FIG. 4 is a block diagram showing a communication circuit in a second communication setting in the first embodiment. [Figure 7] FIG. 4 is a block diagram showing the configuration of a camera and a lens data transmitting / receiving unit in a second communication setting in the first embodiment. [Figure 8] 7A to 7C are diagrams showing waveforms of signals exchanged between the camera body and the interchangeable lens in the second communication setting in the first embodiment. [Figure 9] 5A to 5C are diagrams showing the relationship between data frames exchanged between the camera body and the interchangeable lens in the first communication setting in the first embodiment. [Figure 10] FIG. 11 is a block diagram showing the configuration of a camera system according to a second embodiment of the present invention. [Figure 11]10 is a flowchart showing communication control in the second embodiment. [Figure 12] 10 is a diagram showing waveforms of signals exchanged between a camera body and an interchangeable lens in the second embodiment. [Figure 13] FIG. 11 is a diagram showing an example of setting a predetermined time in a camera system according to a third embodiment of the present invention. [Figure 14] 10 is a flowchart showing communication control in the fourth embodiment of the present invention. [Figure 15] FIG. 13 is a block diagram showing a configuration of a memory controller according to a fourth embodiment. [Figure 16] 13 is a diagram showing waveforms of signals exchanged between a camera body and an interchangeable lens in the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. EXAMPLES

[0021] FIG. 1 shows the configuration of an imaging system (hereinafter, referred to as a camera system) including a camera body 200 as an imaging device according to a first embodiment of the present invention and an interchangeable lens 100 as an accessory device removably attached to the camera body.

[0022] The camera body 200 and the interchangeable lens 100 transmit control commands and internal information via their respective communication units, which will be described later. Each communication unit supports multiple communication formats, and by switching to the same communication format in synchronization with each other depending on the type of data to be communicated and the purpose of the communication, it is possible to select the optimal communication format for various situations.

[0023] First, the specific configurations of the interchangeable lens 100 and the camera body 200 will be described. The interchangeable lens 100 and the camera body 200 are mechanically and electrically connected via a mount 300, which is a coupling mechanism. The interchangeable lens 100 receives power from the camera body 200 via a power terminal section (not shown) provided on the mount 300, and operates various actuators and a lens microcomputer (hereinafter referred to as lens microcomputer) 111, which will be described later. In addition, the interchangeable lens 100 and the camera body 200 communicate with each other via a communication terminal section (shown in FIG. 2) provided on the mount 300.

[0024] The interchangeable lens 100 has an imaging optical system that includes, in order from the subject OBJ side, a field lens 101, a variable magnification lens 102 that changes the magnification, an aperture unit 114 that adjusts the amount of light, an image stabilization lens 103, and a focus lens 104 that adjusts the focus.

[0025] The variable magnification lens 102 and the focus lens 104 are held by lens holding frames 105 and 106, respectively. The lens holding frames 105 and 106 are guided by guide shafts (not shown) so as to be movable in the optical axis direction indicated by the dashed line in the figure, and are driven in the optical axis direction by stepping motors 107 and 108, respectively. The stepping motors 107 and 108 move the variable magnification lens 102 and the focus lens 104, respectively, in synchronization with drive pulses.

[0026] The image stabilization lens 103 reduces image shake caused by camera shake or the like by moving in a direction perpendicular to the optical axis of the imaging optical system.

[0027] The lens microcomputer 111 is an accessory control unit that controls the operation of each unit in the interchangeable lens 100. The lens microcomputer 111 receives control commands transmitted from the camera body 200 via a lens communication unit 112 (lens data transmission / reception unit 112b) serving as an accessory communication unit, and receives a request to transmit lens data (accessory data). The lens microcomputer 111 also performs lens control corresponding to the control command, and transmits lens data corresponding to the transmission request to the camera body 200 via the lens communication unit 112. The lens microcomputer 111 performs operations related to communication with the camera body 200 (a camera microcomputer 205 described later) in accordance with a communication control program serving as a computer program.

[0028] In this embodiment, asynchronous communication is adopted as the communication method between the lens microcomputer 111 and a camera microcomputer (hereinafter referred to as camera microcomputer) 205. The lens microcomputer 111 and the camera microcomputer 205 can share error information indicating the occurrence of a communication abnormality (communication error).

[0029] Furthermore, in response to a command related to magnification change or focusing among the control commands, the lens microcomputer 111 outputs a drive signal to a zoom drive circuit 119 and a focus drive circuit 120 to drive the stepping motors 107, 108. This performs a zoom process for controlling the magnification change operation by the variable magnification lens 102 and an AF (autofocus) process for controlling the focus adjustment operation by the focus lens 104.

[0030] Interchangeable lens 100 has a manual focus ring 130 that can be rotated by a user, and a focus encoder 131 that detects the amount of rotation of manual focus ring 130. Lens microcomputer 111 causes focus drive circuit 120 to drive stepping motor 108 in accordance with the amount of rotation of manual focus ring 130 detected by focus encoder 131, thereby moving focus lens 104. This performs MF (manual focus).

[0031] The aperture unit 114 is configured to include aperture blades 114a and 114b. The states of the aperture blades 114a and 114b are detected by a Hall element 115 and input to the lens microcomputer 111 via an amplifier circuit 122 and an A / D conversion circuit 123. The lens microcomputer 111 outputs a drive signal to an aperture drive circuit 121 based on an input signal from the A / D conversion circuit 123 to drive the aperture actuator 113. This controls the light amount adjustment operation by the aperture unit 114.

[0032] Furthermore, the lens microcomputer 111 drives an anti-shake actuator 126 via an anti-shake drive circuit 125 in response to shake detected by a shake sensor (not shown) such as a vibration gyroscope provided in the interchangeable lens 100. This performs anti-shake processing that controls the movement of the image stabilization lens 103.

[0033] The camera body 200 has an imaging element 201 such as a CCD sensor or a CMOS sensor, an A / D conversion circuit 202, a signal processing circuit 203, a recording unit 204, a camera microcomputer (hereinafter referred to as a camera microcomputer) 205, and a display unit 206.

[0034] The image sensor 201 photoelectrically converts an object image formed by the imaging optical system in the interchangeable lens 100 and outputs an electrical signal (analog signal). The A / D conversion circuit 202 converts the analog signal from the image sensor 201 into a digital signal. The signal processing circuit 203 performs various image processing on the digital signal from the A / D conversion circuit 202 to generate a video signal. The signal processing circuit 203 also generates, from the video signal, focus information indicating the contrast state of the object image, that is, the focus state of the imaging optical system, and luminance information indicating the exposure state. The signal processing circuit 203 outputs the video signal to a display unit 206, and the display unit 206 displays the video signal as a live view image used to check the composition, focus state, and the like. The signal processing circuit 203 also outputs the video signal to a recording unit 204, and the recording unit 204 records the video signal.

[0035] The memory (storage unit) 210 is configured with a DDR (Double Data Rate SDRAM) etc. The memory 210 stores a digital imaging signal obtained by the imaging element 201 or a video signal generated by the image processing circuit 203, and stores lens data received from the lens microcomputer 111.

[0036] The camera microcomputer 205 as a camera control unit controls the camera body 200 in response to input from a camera operation unit 207 including an image capture instruction switch and various setting switches (not shown). The camera microcomputer 205 also transmits a control command related to the magnification change operation of the zoom lens 102 to the lens microcomputer 111 in response to the operation of a zoom switch (not shown) via the camera communication unit 208 (camera data transmission / reception unit 208b). The camera microcomputer 205 also transmits a control command related to the light amount adjustment operation of the aperture unit 114 in response to brightness information and the focus adjustment operation of the focus lens 104 in response to focus information to the lens microcomputer 111 via the camera communication unit 208. The camera microcomputer 205 performs operations related to communication with the lens microcomputer 111 in accordance with a communication control program as a computer program.

[0037] Next, a communication circuit configured between the camera body 200 (camera microcomputer 205) and the interchangeable lens 100 (lens microcomputer 111) and the communication carried out between them will be described with reference to Fig. 2. The camera microcomputer 205 has a function of managing the communication method and communication settings with the lens microcomputer 111, and a function of sending notifications such as transmission requests to the lens microcomputer 111. In addition, the lens microcomputer 111 has a function of generating lens data and a function of transmitting the lens data.

[0038] The camera microcomputer 205 has a camera communication interface circuit 208a, and the lens microcomputer 111 has a lens communication interface circuit 112a. The camera microcomputer 205 (camera data transmission / reception unit 208b) and the lens microcomputer 111 (lens data transmission / reception unit 112b) communicate with each other via a communication terminal unit (shown as three squares in the figure) provided on the mount 300 and the communication interface circuits 208a and 112a. In this embodiment, the camera microcomputer 205 and the lens microcomputer 111 perform asynchronous serial communication using three channels (three-wire type). The camera data transmission / reception unit 208b and the camera communication interface circuit 208a constitute the camera communication unit 112, and the lens data transmission / reception unit 112b and the lens communication interface circuit 112a constitute the lens communication unit 112 as an accessory communication unit.

[0039] The above three channels are composed of a transmission request channel as a notification channel, a first data communication channel, and a second data communication channel. The transmission request channel is used for notifications such as a transmission request (transmission instruction) for lens data from the camera microcomputer 205 to the lens microcomputer 111 and a request (switching instruction) for switching communication settings described below. Notification on the transmission request channel is performed by switching the level (voltage level) of the signal on the transmission request channel between High (first level) and Low (second level). In the following description, the signal supplied to the transmission request channel is referred to as a transmission request signal RTS.

[0040] The first data communication channel is used to transmit lens data from the lens microcomputer 111 to the camera microcomputer 205. In the following description, the lens data (accessory data) transmitted as a signal from the lens microcomputer 111 to the camera microcomputer 205 on the first data communication channel is referred to as a lens data signal DLC. The second data communication channel is used to transmit camera data from the camera microcomputer 205 to the lens microcomputer 111. In the following description, the camera data transmitted as a signal from the camera microcomputer 205 to the lens microcomputer 111 on the second data communication channel is referred to as a camera data signal DCL.

[0041] The transmission request signal RTS is sent from the camera microcomputer 205 as the communication master to the lens microcomputer 111 as the communication slave. The camera data signal DCL includes a control command, a transmission request command, etc., from the camera microcomputer 205 to the lens microcomputer 111. The lens data signal DLC includes various data transmitted from the lens microcomputer 111 to the camera microcomputer 205. The camera microcomputer 205 and the lens microcomputer 111 set a communication speed in advance, and transmit and receive data at a communication bit rate according to this setting. The communication bit rate indicates the amount of data that can be transferred per second, and is expressed in units of bps (bits per second). The camera microcomputer 205 and the lens microcomputer 111 communicate with each other in a full-duplex communication method (full-duplex method) in which they transmit and receive data to each other.

[0042] Note that, instead of the asynchronous serial communication using three channels, clock synchronous serial communication using three channels may be performed. Also, when the amount of data transmitted from the lens microcomputer 111 to the camera microcomputer 205 is large, the clock synchronous serial communication may be switched to the asynchronous serial communication. In this case, the notification channel may be used as a clock line that supplies a clock signal LCLK from the camera microcomputer 205 to the lens microcomputer 111. This makes it possible to switch between the two communication methods of asynchronous serial communication and clock synchronous serial communication without adding a new channel.

[0043] In clock synchronous serial communication using three channels, a clock signal LCLK is output from the camera microcomputer 205 as a communication master to the lens microcomputer 111 as a communication slave via the clock channel. The camera data signal DCL includes control commands and transmission request commands from the camera microcomputer 205 to the lens microcomputer 111. Meanwhile, the lens data signal DLC includes various data transmitted from the lens microcomputer 111 to the camera microcomputer 205 in synchronization with the clock signal LCLK. In clock synchronous serial communication, the camera microcomputer 205 and the lens microcomputer 111 communicate with each other using a full-duplex communication method in which they transmit and receive data to each other in synchronization with a common clock signal LCLK.

[0044] Next, a first communication setting, which is a communication setting between the camera microcomputer 205 and the lens microcomputer 111, will be described with reference to Figs. 3 to 5 and 9. Fig. 3 shows the configuration of the camera data transmission / reception unit 208b in the camera microcomputer 205 and the lens data transmission / reception unit 112b in the lens microcomputer 111. Reference numeral 205a denotes a CPU serving as the main body of the camera microcomputer 205. Reference numeral 301 denotes an RTS control unit, and reference numeral 302 denotes a transmission data buffer (camera data buffer) constituted by a RAM or the like. Reference numeral 303 denotes a reception data buffer constituted by a RAM or the like, and reference numeral 304 denotes a buffer control unit that controls the storage of data in and the reading of data from the buffers 302 and 303.

[0045] 3 shows the configuration of camera data transmission / reception 208b in camera microcomputer 205 in camera body 200. Reference numeral 205a denotes a CPU serving as the main body of camera microcomputer 205. Reference numeral 301 denotes an RTS control unit, and reference numeral 302 denotes a transmission data buffer constituted by RAM or the like. Reference numeral 303 denotes a reception data buffer constituted by RAM or the like, and reference numeral 304 denotes a buffer control unit that controls the storage of data in and the reading of data from buffers 302 and 303.

[0046] Meanwhile, within the lens microcomputer 111, reference numeral 111a denotes a CPU serving as the main body of the lens microcomputer 111. Reference numeral 316 denotes an RTS detection unit, and reference numeral 311 denotes a received data buffer constituted by a RAM or the like. Reference numeral 312 denotes a transmitted data buffer (accessory data buffer) constituted by a RAM or the like, and reference numeral 313 denotes a buffer control unit that controls the storage of data in and the reading of data from the buffers 311 and 312.

[0047] The camera data signal DCL transmitted from the camera microcomputer 205 to the lens microcomputer 111 is stored in the transmission data buffer 302. For example, when transmitting a 128-byte camera data signal DCL, the 128-byte camera data signal DCL is stored in the transmission data buffer 302 before transmission starts. The buffer control unit 304 reads out the camera data signal DCL to be transmitted from the transmission data buffer 302 for each frame. Then, the read camera data signal DCL for each frame is converted from a parallel data signal to a serial data signal by the parallel-serial conversion unit 305, and transmitted to the lens microcomputer 111 through the second data communication channel.

[0048] The camera data signal DCL transmitted from the camera microcomputer 205 is converted from a serial data signal to a parallel data signal by a serial-parallel conversion unit 314 in the lens microcomputer 111. The buffer control unit 313 stores the camera data signal DCL converted into the parallel data signal in the received data buffer 311.

[0049] The lens data signal DLC transmitted from the lens microcomputer 111 to the camera microcomputer 205 is stored in the transmission data buffer 312. For example, when transmitting a 128-byte lens data signal DLC, the transmission is started after storing the 128-byte lens data signal DLC in the transmission data buffer 312. The buffer control unit 313 reads out the lens data signal DLC to be transmitted from the transmission data buffer 312 for each frame. Then, the lens data signal DLC read out for each frame is converted from a parallel data signal to a serial data signal by the parallel-serial conversion unit 315 and transmitted to the camera microcomputer 205 through the first data communication channel.

[0050] The lens data signal DLC transmitted from the lens microcomputer 111 is converted from a serial data signal to a parallel data signal by a serial-parallel conversion unit 306 in the camera microcomputer 205. The buffer control unit 304 stores the lens data signal DLC converted into a parallel data signal in the received data buffer 303. The lens data signal DLC stored in the received data buffer 303 is read out from the received data buffer 303 by the DMA control unit 307, and the read data is transferred to and stored in the memory 210.

[0051] As will be further explained below, this first communication setting includes a communication setting in which a BUSY frame is added (hereinafter referred to as a BUSY addition mode) and a communication setting in which a BUSY frame is not added (hereinafter referred to as a non-BUSY addition mode). Figures 4(A) to (C) show waveforms of signals exchanged between the camera microcomputer 205 and the lens microcomputer 111 in the first communication setting. The procedure for this exchange is called a communication protocol.

[0052] 4A shows the signal waveform of one frame, which is the unit of communication. The data format of one frame differs in part between the lens data signal DLC and the camera data signal DCL.

[0053] First, the data format of the lens data signal DLC will be explained. One frame of the lens data signal DLC is broadly divided into a first half data frame and a following BUSY frame. The lens data signal DLC maintains a high signal level when in a non-transmission state where no data is being transmitted.

[0054] The lens microcomputer 111 sets the signal level of the lens data signal DLC to Low for one bit period in order to notify the camera microcomputer 205 of the start of transmission of one frame of the lens data signal DLC. This one bit period is called a start bit ST, which indicates the start of one frame. In other words, a data frame starts from this start bit ST. The start bit ST is provided at the first bit of each frame of the lens data signal DLC.

[0055] Next, the lens microcomputer 111 transmits one byte of lens data in the next 8-bit period from the second bit to the ninth bit. The data is arranged in MSB-first format, starting with the most significant data D7, followed by data D6, data D5, and ending with the least significant data D0. The lens microcomputer 111 then adds one bit of parity information PA to the tenth bit, and sets the signal level of the lens data signal DLC to High during the stop bit SP period indicating the end of one frame. This ends the data frame period that began with the start bit ST.

[0056] Next, as indicated by "DLC (BUSY)" in the figure, the lens microcomputer 111 adds a BUSY frame after the stop bit SP. The BUSY frame indicates the period of the communication standby request BUSY notified from the lens microcomputer 111 to the camera microcomputer 205. The lens microcomputer 111 holds the signal level of the lens data signal DLC low until the communication standby request BUSY is released.

[0057] On the other hand, there are cases where it is not necessary to notify the camera microcomputer 205 of the communication standby request BUSY from the lens microcomputer 111. For such cases, as shown in "DLC (no BUSY)" in the figure, a data format is also provided that configures one frame without adding a BUSY frame (hereinafter also referred to as a BUSY notification). In other words, the data format of the lens data signal DLC can be selected to have a BUSY notification added or not added depending on the processing status on the lens microcomputer side.

[0058] A method of identifying the presence or absence of a BUSY notification performed by the camera microcomputer 205 will be described. The signal waveform shown in "DLC (no BUSY)" in FIG. 4A and the signal waveform shown in "DLC (BUSY present)" in FIG. 4A include bit positions B1 and B2. The camera microcomputer 205 selects either the B1 or B2 bit position as the BUSY identification position P for identifying the presence or absence of a BUSY notification. In this manner, this embodiment employs a data format in which the BUSY identification position P is selected from the B1 and B2 bit positions. This makes it possible to address the issue that the processing time required to determine a BUSY notification (DLC Low) after transmitting a data frame of the lens data signal DLC differs depending on the processing performance of the lens microcomputer 111. Whether the BUSY identification position P is the bit position of B1 or the bit position of B2 is determined by communication between the camera microcomputer 205 and the lens microcomputer 111 before communication is performed. Note that the BUSY identification position P does not need to be fixed to either the bit position of B1 or B2, and may be changed depending on the processing capabilities of both microcomputers 205, 111.

[0059] Fig. 4(B) shows signal waveforms when continuous communication is performed in the BUSY-added mode shown in "DLC (with BUSY)" in Fig. 4(A). A communication standby request BUSY (BUSY frame) from the lens microcomputer 111 is notified using a lens data signal DLC in the first data communication channel, and the next communication is started after the communication standby request BUSY is released. CMD1 shown in Fig. 4(B) shows a transmission request command transmitted from the camera microcomputer 205 to the lens microcomputer 111 as a camera data signal DCL. In response to receiving this transmission request command CMD1, the lens microcomputer 111 transmits a 2-byte lens data signal DT1 (DT1a, DT1b) corresponding to the transmission request command CMD1 to the camera microcomputer 205.

[0060] FIG. 4C shows signal waveforms when communication is performed by switching between the BUSY addition mode and the non-BUSY addition mode. In the example of FIG. 4C, communication is performed first in the BUSY addition mode, and then in the non-BUSY addition mode. CMD2 shows a control command and a transmission request command transmitted from the camera microcomputer 205 to the lens microcomputer 111 as a camera data signal DCL. Although the figure shows a case where the control command and the transmission request command are transmitted in one frame, the control command and the transmission request command may be transmitted in separate frames. In response to receiving a control command from the command CMD2, the lens microcomputer 111 switches the communication setting (communication mode) from the BUSY addition mode to a mode in which a BUSY frame is not added. In response to receiving a transmission request command from the command CMD2, the lens microcomputer 111 transmits a 3-byte lens data signal DT2 (DT2a to DT2c) corresponding to the transmission request command to the camera microcomputer 205.

[0061] Next, the data format of the camera data signal DCL will be described. The specifications of one data frame are the same as those of the lens data signal DLC. However, unlike the lens data signal DLC, the camera data signal DCL prohibits the addition of a BUSY frame.

[0062] Next, a description will be given of a procedure for communication in the first communication setting between the camera microcomputer 205 and the lens microcomputer 111. First, a description will be given of a procedure for communication in the BUSY additional mode.

[0063] When an event occurs that starts communication with the lens microcomputer 111, the camera microcomputer 205 notifies the lens microcomputer 111 of a transmission request by setting the level of the transmission request signal RTS to Low (hereinafter, referred to as asserting the transmission request signal RTS). When the lens microcomputer 111 detects a transmission request by the Low level of the transmission request signal RTS, it performs a process of generating a lens data signal DLC to be transmitted to the camera microcomputer 205. Then, when the lens data signal DLC is ready to be transmitted, it starts transmitting one frame of the lens data signal DLC through the first data communication channel. Here, the lens microcomputer 111 may start transmitting the lens data signal DLC within a set time mutually set between the camera microcomputer 205 and the lens microcomputer 111 from the time the transmission request signal RTS goes Low. In other words, there is no strict restriction that the lens data to be transmitted must be determined by the time the first clock pulse is input between the time the transmission request signal RTS goes Low and the start of transmission of the lens data signal DLC.

[0064] Next, the camera microcomputer 205 returns the level of the transmission request signal RTS to High in response to detection of the start bit ST, which is the first bit of the data frame of the lens data signal DLC received from the lens microcomputer 111 (hereinafter referred to as negating the transmission request signal RTS). This cancels the transmission request and starts transmitting the camera data signal DCL on the second data communication channel. Note that it does not matter which comes first, the negation of the transmission request signal RTS or the start of transmission of the camera data signal DCL, as long as these are performed before the reception of the data frame of the lens data signal DLC is completed.

[0065] The lens microcomputer 111, which has transmitted the data frame of the lens data signal DLC, adds a BUSY frame to the lens data signal DLC when it is necessary to notify the camera microcomputer 205 of a communication standby request BUSY. The camera microcomputer 205 monitors whether or not a communication standby request BUSY has been notified, and is prohibited from asserting a transmission request signal RTS for the next transmission request while the communication standby request BUSY is being notified. The lens microcomputer 111 executes necessary processing during the period in which communication from the camera microcomputer 205 is being held in abeyance due to the communication standby request BUSY, and releases the communication standby request BUSY after preparations for the next communication are complete. The camera microcomputer 205 is permitted to assert a transmission request signal RTS for the next transmission request on the condition that the communication standby request BUSY has been released and transmission of the data frame of the camera data signal DCL has been completed.

[0066] Thus, in this embodiment, when a communication start event in the camera microcomputer 205 triggers the assertion of the transmission request signal RTS, the lens microcomputer 111 starts transmitting a data frame of the lens data signal DLC to the camera microcomputer 205. Then, when the camera microcomputer 205 detects the start bit ST of the lens data signal DLC, it starts transmitting a data frame of the camera data signal DCL to the lens microcomputer 111. Here, the lens microcomputer 111 adds a BUSY frame after the data frame of the lens data signal DLC to request communication standby BUSY as necessary, and then cancels the communication standby request BUSY to complete communication processing for one frame. Through this communication processing, one byte of data is transmitted and received between the camera microcomputer 205 and the lens microcomputer 111.

[0067] Next, the procedure for communication in the non-BUSY additional mode will be described. The non-BUSY additional mode allows faster data communication than the BUSY additional mode because no BUSY frame is added.

[0068] Fig. 5(A) shows the waveform of a signal exchanged between the camera microcomputer 205 and the lens microcomputer 111 in the non-BUSY added mode. Fig. 5(A) shows the signal waveform when three frames, each of which is the minimum communication unit, are communicated consecutively. As described above, in the non-BUSY added mode, the communication standby request BUSY is not added to the lens data signal DLC.

[0069] In the non-BUSY added mode, the data format of the lens data signal DLC is such that one frame is composed only of a data frame, and no BUSY frame exists. For this reason, in the non-BUSY added mode, the lens microcomputer 111 cannot notify the camera microcomputer 205 of a communication standby request BUSY. This type of data format is used for continuous communication (burst communication) with short intervals between frames when transferring a relatively large amount of data between the camera microcomputer 205 and the lens microcomputer 111. In other words, the non-BUSY added mode enables high-speed communication of large amounts of data.

[0070] In addition, in the non-BUSY addition mode, the number of stop bits SP, which are the last bits of each frame of the lens data signal DLC, is set to 2, which is more than the number of stop bits ST of each frame of the camera data signal DCL. This difference in the number of stop bits makes the bit length of one frame of the lens data signal DLC longer than the bit length of one frame of the camera data signal DCL. The purpose of this will be described later.

[0071] Fig. 5(B) shows signal waveforms when the camera microcomputer 205 and the lens microcomputer 111 continuously transmit and receive n frames of the camera data signal DCL and the lens data signal DLC, respectively (i.e., when performing burst communication). Prior to the start of this communication, the camera microcomputer 205 has been notified of n frames, which is data size information (number of frames) to be transmitted, from the lens microcomputer 111 through the communication of one frame of the camera data signal DCL shown in Fig. 4(A).

[0072] The camera microcomputer 205 asserts the transmission request signal RTS when an event occurs that starts communication with the lens microcomputer 111. Thereafter, in the non-BUSY added mode, unlike the BUSY added mode, the camera microcomputer 205 does not need to negate the transmission request signal RTS every frame, and maintains the asserted state of the transmission request signal RTS while continuous data transmission and reception is possible.

[0073] When the lens microcomputer 111 detects a transmission request by asserting the transmission request signal RTS, it performs processing to generate a lens data signal DLC to be transmitted to the camera microcomputer 205. Then, when preparations for transmitting the lens data signal DLC are complete, it starts transmitting the first frame DL1 of the lens data signal DLC over the first data communication channel.

[0074] After transmitting the data frame of the first frame of the lens data signal DLC, the lens microcomputer 111 checks the transmission request signal RTS again. At this time, if the transmission request signal RTS is in an asserted state, the lens microcomputer 111 transmits the second frame DL2 of the next lens data signal DLC to the camera microcomputer 205 following the first frame whose transmission has been completed. In this manner, while the asserted state of the transmission request signal RTS is maintained, the lens data signal DLC (DL1 to DLn) from the lens microcomputer 111 is continuously transmitted to the camera microcomputer 205. Then, when the transmission of the number of frames n indicated in the data size information is completed, the transmission of the lens data signal DLC is stopped.

[0075] The camera microcomputer 205 transmits n frames of the camera data signal DCL (DC1 to DCn) through the second data communication channel in response to detecting the start bit ST for each frame of the lens data signal DCL from the lens microcomputer 111. In this manner, the camera microcomputer 205 maintains the asserted state of the transmission request signal RTS, thereby enabling continuous transmission and reception of the lens data signal DLC and the camera data signal DCL for the number of frames corresponding to the data size information.

[0076] The camera microcomputer 205 temporarily stores the lens data signal DLC continuously received from the lens microcomputer 111 in the received data buffer 303 via a serial-parallel conversion unit 306. The DMA control unit 307 transfers the lens data signal DLC stored in the received data buffer 303 to the memory 210, and finally stores it in the memory 210. For this reason, when receiving a lens data signal DLC whose amount of data exceeds the capacity of the received data buffer 303, it is necessary to transfer the lens data signal DLC previously stored in the received data buffer 303 to the memory 210 and ensure free capacity in the buffer 303.

[0077] However, if the DMA control unit 307 cannot access the memory 210 due to the processing status of the signal processing circuit 203 provided in the camera body 200, the lens data signal DLC continuously received from the lens microcomputer 111 cannot be transferred to the memory 210. As a result, free space cannot be secured in the received data buffer 303, and a part of the continuously received lens data signal DLC cannot be stored in the memory 210. For example, data of the lens data signal DLC already received by the camera microcomputer 205 that has not been transferred to the memory 210 and remains in the received data buffer 303 is overwritten by data received later, resulting in data not being stored in the memory 210. Therefore, it is necessary to temporarily stop the communication being performed between the camera microcomputer 205 and the lens microcomputer 111 before the data stored in the received data buffer 303 is overwritten.

[0078] Fig. 5(C) shows signal waveforms when a temporary communication stop is instructed by the camera microcomputer 205 or the lens microcomputer 111 during the continuous data transmission and reception communication shown in Fig. 5(B). Here too, the lens microcomputer 111 starts transmitting the lens data signal DLC when the camera microcomputer 205 asserts a transmission request signal RTS, and the camera microcomputer 205 starts transmitting the camera data signal DCL in response to detection of the start bit ST.

[0079] T2w1 indicates a communication stop period during which a communication stop instruction is given by the camera microcomputer 205. The instruction is notified to the lens microcomputer 111 by the camera microcomputer 205 temporarily negating the transmission request signal RTS. When the lens microcomputer 111 detects that the transmission request signal RTS has been negated, it stops the transmission after completing the transmission of the frame of the lens data signal DLC (DL6 in the figure: hereinafter referred to as the stop frame) that was being transmitted at the time of detection. In response to this stop of transmission of the lens data signal DLC, the camera microcomputer 205 also stops the transmission of the camera data signal DCL after transmitting a frame (DC6) of the camera data signal DCL that corresponds to the stop frame. With this communication control, even if a communication stop instruction is given during communication of continuous data transmission and reception, it is possible to manage the number of transmitted frames of the lens data signal DLC and the camera data signal DCL to be the same (synchronized).

[0080] When the event requesting stop of communication disappears, the camera microcomputer 205 can instruct the lens microcomputer 111 to restart communication by reasserting the transmission request signal RTS. In response to the instruction to restart communication, the lens microcomputer 111 restarts transmission of the lens data signal DLC from the frame next to the stop frame (DL7: hereinafter referred to as the restart frame). Then, in response to detection of the start bit ST of the restart frame, the camera microcomputer 205 restarts transmission of the camera data signal DCL from the frame (DC7) corresponding to the above-mentioned restart frame.

[0081] In this way, the camera microcomputer 205 stops communication with the lens microcomputer 111 by temporarily negating the transmission request signal RTS. Then, if the number of frames of the lens data signal DLC received at that point is less than the number of frames indicated in the data size information, the camera microcomputer 205 can resume receiving the lens data signal DLC from the lens microcomputer 111 by re-asserting the transmission request signal RTS.

[0082] After the end of the communication suspension period T2w1, neither the camera microcomputer 205 nor the lens microcomputer 111 instructs or notifies the suspension of communication, and continuous data communication is performed in the order of the above-mentioned restart frames DL7, DC7 and the subsequent frames DL8, DC8 to DL9, DC9.

[0083] Then, when transmission of frame DL9 (reception of frame DC9 by the camera microcomputer 205) is completed within the lens microcomputer 111, a communication stop request event occurs, causing the lens microcomputer 111 to notify the camera microcomputer 205 of a communication stop. This notification is made by the lens microcomputer 111 notifying the camera microcomputer 205 of a communication stop by not transmitting the lens data signal DLC even if the transmission request signal RTS is in an asserted state. T2w2 represents the communication stop period during which the lens microcomputer 111 notifies the communication stop.

[0084] The camera microcomputer 205 constantly monitors the start bit ST for each frame of the lens data signal DLC, and if it does not detect the start bit ST, it is arranged to stop transmitting the next frame of the camera data signal DCL. Therefore, even if the camera microcomputer 205 asserts the transmission request signal RTS, if it does not receive the lens data signal DLC (DL10 in the figure) from the lens microcomputer 111, it stops communication without transmitting the camera data signal DCL (DC10) to the lens microcomputer 111. Note that the camera microcomputer 205 maintains the transmission request signal RTS in an asserted state during the communication suspension period T2w2 instructed by the lens microcomputer 111.

[0085] Thereafter, the communication stop request event disappears in the lens microcomputer 111, and the lens microcomputer 111 resumes transmission of the resume frame DL10 of the lens data signal DLC. In response to detecting the start bit ST of the resume frame DL10, the camera microcomputer 205 resumes transmission of the corresponding frame DC10 in the camera data signal DCL.

[0086] Next, a problem that may occur when there is a difference between the bit rate of the camera data signal DCL output by the camera microcomputer 205 and the bit rate of the lens data signal DLC output by the lens microcomputer 111 in the non-BUSY added mode will be described with reference to Fig. 9(A). Fig. 9(A) shows the relationship between the frames of the camera data signal DCL and the lens data signal DLC when the bit length of one frame (data frame) of both the camera data signal DCL and the lens data signal DLC is the same and the bit rate of the camera data signal DCL is slower than that of the lens data signal DLC. The arrows in the figure indicate which start bit ST in the lens data signal DLC the camera microcomputer 205 detects and which frame in the camera data signal DCL is transmitted to the lens microcomputer 111.

[0087] Since the bit rate of the camera data signal DCL is slower than that of the lens data signal DLC, the delay of the frames of the camera data signal DCL gradually increases with respect to the frames of the lens data signal DLC. Since continuous data communication is performed, there is no gap (non-communication time) between the frames. Therefore, as the delay accumulates, the difference between the two data signals DCL and DLC becomes one frame or more, and a difference occurs in the number of transmitted frames of the two data signals DCL and DLC. In addition, the camera microcomputer 205 detects the start bit ST of the lens data signal DLC by skipping one frame, resulting in a period of about one frame during which the camera data signal DCL is not transmitted. When such a situation occurs, it becomes difficult to manage the number of communication data between the camera microcomputer 205 and the lens microcomputer 111, and data communication breaks down.

[0088] Therefore, in this embodiment, as shown in FIG. 5(A) and FIG. 9(B), the number of stop bits SP, which are the last bits per frame of the lens data signal DLC, is made larger than the number of stop bits ST per frame of the camera data signal DCL. Specifically, the number of stop bits ST per frame of the camera data signal DCL is 1, while the number of stop bits SP per frame of the lens data signal DLC is 2. Except for the difference in the number of stop bits, the data format of the lens data signal DLC and the data format of the camera data signal DCL are the same. Due to this difference in the number of stop bits, the number of bits per frame (of the data frame) of the lens data signal DLC becomes larger than the number of bits per frame of the camera data signal DCL. In other words, the bit length of one frame of the lens data signal DLC becomes longer than the bit length of one frame of the camera data signal DCL. This makes it possible to prevent the accumulation of frame shifts of the camera data signal DCL with respect to the frames of the lens data signal DLC, even if the bit rate of the camera data signal DCL is slower than that of the lens data signal DLC signal.

[0089] Since the bit length of one frame of the lens data signal DLC is longer than the bit length of one frame of the camera data signal DCL, if the bit rates of both data signals DCL and DLC are the same, the camera data signal DCL will be completed transmission earlier. Furthermore, even if the bit rate of the camera data signal DCL is slower than that of the lens data signal DLC due to a bit rate error, the 1 bit as the bit length difference of one frame is a sufficient margin to absorb the difference in transmission time for each frame due to the bit rate error.

[0090] If the bit rate of the camera data signal DCL is faster than that of the lens data signal DLC, the above-mentioned problem of frame misalignment does not occur. This is because the frame of the camera data signal DCL is set to be transmitted in response to detection of the start bit ST of the frame of the lens data signal DLC. Even if the bit rates that can be set in the camera body 200 and the interchangeable lens 100 are slightly different, it is possible to deal with this by further increasing the number of bits of the stop bit SP of the lens data signal DLC.

[0091] As described above, in this embodiment, in the BUSY-added mode in the first communication setting, the camera microcomputer 205 can notify the lens microcomputer 111 of the end of communication by negating the transmission request signal RTS. Also, the lens microcomputer 111 can notify the camera microcomputer 205 of the end of communication by adding a communication standby request BUSY (BUSY frame) to the lens data signal DLC. This allows the camera microcomputer 205 and the lens microcomputer 111 to communicate data smoothly and at high speed. On the other hand, in the non-BUSY-added mode in the first communication setting, the camera microcomputer 205 can notify the lens microcomputer 111 of the end of communication by negating the transmission request signal RTS during burst communication from the lens microcomputer 111 to the camera microcomputer 205. This allows large amounts of data to be communicated at high speed between the camera microcomputer 205 and the lens microcomputer 111 while maintaining synchronization.

[0092] Next, the second communication setting between the camera microcomputer 205 and the lens microcomputer 111 will be described. In the second communication setting, as shown in FIG. 6, the second data communication channel is used to transmit lens data from the lens microcomputer 111 to the camera microcomputer 205 by switching the communication direction (communication setting) in the communication interface circuits 208a, 112a. That is, the signal circuit of the second data communication channel is configured with input / output buffers in parallel so that the input / output direction can be switched, and each can be exclusively selected. In the following description, the lens data transmitted as a signal from the lens microcomputer 111 to the camera microcomputer 205 through the second data communication channel is referred to as the second lens data signal DLC2. In addition, the lens data signal DLC transmitted from the lens microcomputer 111 to the camera microcomputer 205 through the first data communication channel together with the transmission of the second lens data signal DLC2 is referred to as the first lens data signal DLC to distinguish it from the second lens data signal DLC2.

[0093] In the second communication setting, both the first and second data communication channels are used for continuous communication (burst communication) of the lens data signal to the camera microcomputer 205. This enables communication of a large amount of data at higher speeds than in the non-BUSY additional mode in the first communication setting.

[0094] However, when switching from the first communication setting to the second communication setting, it is necessary to avoid collision between the camera data signal DCL transmitted from the camera microcomputer 205 and the lens data signal DLC2 transmitted from the lens microcomputer 111 on the second data communication channel. For this reason, in this embodiment, the camera microcomputer 205 and the lens microcomputer 111 perform a communication setting switching process as described below.

[0095] 7 shows the configuration of the camera data transmission / reception unit 208b in the camera microcomputer 205 and the lens data transmission / reception unit 112b in the lens microcomputer 111. In FIG. 7, components common to those shown in FIG. 3 are denoted by the same reference numerals as in FIG. 3, and their description will not be repeated. In the camera data transmission / reception unit 208b, 1401 is a communication direction switching unit. The communication direction switching unit 1401 switches the communication direction of the second data communication channel to a direction in which the camera microcomputer 205 receives the second lens data signal DLC2 transmitted from the lens microcomputer 111, by switching a switch 1402. Thereafter, the camera microcomputer 205 converts the second lens data signal DLC2 received from the lens microcomputer 111 via the second data communication channel from serial data to parallel data in the serial-parallel conversion unit 306, and stores the converted data in the received data buffer 303. The received data buffer 303 also stores a first lens data signal DLC that is received via the first data communication channel and converted from serial data to parallel data by the serial-parallel converter 306. The second lens data signal DLC2 stored in the received data buffer 303 is read out by the DMA controller 307 and transferred to and stored in the memory 210.

[0096] In the lens data transmission / reception unit 112b, 1411 is a communication direction switching unit. The communication direction switching unit 1411 switches the communication direction of the second data communication channel to a direction in which the lens microcomputer 111 transmits the second lens data signal DLC2 to the camera microcomputer 205 by switching the switch 1412. After this, the lens microcomputer 111 converts the second lens data signal DLC2 stored in the transmission data buffer 312 from parallel data to serial data in the parallel-serial conversion unit 315, and transmits it to the camera microcomputer 205 through the second data communication channel. Note that the lens microcomputer 111 converts the first lens data signal DLC stored in the transmission data buffer 312 from parallel data to serial data in the parallel-serial conversion unit 315, and transmits it to the camera microcomputer 205 through the first data communication channel.

[0097] Next, the procedure of communication in the second communication setting will be described. Fig. 8(A) shows the waveforms of signals exchanged between the camera microcomputer 205 and the lens microcomputer 111 in the second communication setting. Fig. 8(A) shows the signal waveforms when three frames, each of which is the minimum communication unit, are communicated consecutively.

[0098] In the second communication setting, each frame of the first and second lens data signals DLC, DLC2 is composed of only data frames, and no BUSY frames exist, similar to the non-BUSY added mode in the first communication setting. In other words, the first and second lens data signals DLC, DLC2 have a data format that does not allow the lens microcomputer 111 to notify the camera microcomputer 205 of a communication standby request BUSY. In addition, the second communication setting is specialized as a communication setting used only for data transfer from the lens microcomputer 111 to the camera microcomputer 205, and data transfer from the camera microcomputer 205 to the lens microcomputer 111 is not possible in this second communication setting. In addition, the first and second lens data signals DLC, DLC2 have a data format that allows continuous communication without leaving an interval between the stop bit SP of the previous frame and the start bit ST of the next frame, similar to the non-BUSY added mode in the first communication setting.

[0099] The data frames of the first and second lens data signals DLC, DLC2 have the same data format and the bit length of one frame is the same. This is for the purpose of managing the transmitted frames as if they were the same if a stop occurs during communication. However, the relative relationship of the bit positions of the data frames of the first and second lens data signals DLC, DLC2 does not necessarily need to be the same, and any deviation in the bit positions between them is permissible as long as it does not exceed the length of one frame.

[0100] Figure 8 (B) shows the signal waveform when, in the second communication setting, the lens microcontroller 111 continuously transmits a total of n frames of the first and second lens data signals DLC, DLC2 to the camera microcontroller 205 (i.e., when performing burst communication).

[0101] The camera microcomputer 205 asserts a request-to-send signal RTS when an event occurs that starts communication with the lens microcomputer 111. Thereafter, the camera microcomputer 205 does not need to negate the request-to-send signal RTS for each frame, and maintains the asserted state of the request-to-send signal RTS while data transmission and reception is possible continuously.

[0102] When the lens microcomputer 111 detects a transmission request by asserting the transmission request signal RTS, it performs processing to generate the first and second lens data signals DLC, DLC2 to be transmitted to the camera microcomputer 205. Then, when preparations for transmitting the first and second lens data signals DLC, DLC2 are complete, it starts transmitting the first frame DL1 of the first lens data signal DLC to the camera microcomputer 205 via the first data communications channel. At the same time, it starts transmitting the second frame DL2 of the second lens data signal DLC2 to the camera microcomputer 205 via the second data communications channel.

[0103] After completing the transmission of the first and second frames DL1, DL2 of the first and second lens data signals DLC, DLC2, the lens microcomputer 111 checks the state of the transmission request signal RTS. If the transmission request signal RTS is in an asserted state, the lens microcomputer 111 starts transmitting the third and fourth frames DL3, DL4 of the first and second lens data signals DLC, DLC2 to the camera microcomputer 205 following the first and second frames. In this way, the camera microcomputer 205 maintains the asserted state of the transmission request signal RTS, allowing the lens microcomputer 111 to continuously transmit a total of n frames of the first and second lens data signals DLC, DLC2 to the camera microcomputer 205.

[0104] By setting the total number of frames n of the first and second lens data signals DLC, DLC2 to an even number, the number of frames transmitted from the lens microcomputer 111 to the camera microcomputer 205 via the first and second data communication channels will be the same. Note that in Fig. 8(B) the first lens data signal DLC transmitted via the first data communication channel is made up of only odd-numbered frames, and the second lens data signal DLC2 transmitted via the second data communication channel is made up of only even-numbered frames. However, the first and second lens data signals DLC, DLC2 may have a frame configuration other than this.

[0105] Fig. 8(C) shows signal waveforms when the camera microcomputer 205 and the lens microcomputer 111 each instruct the lens microcomputer 111 to stop communication during the continuous transmission of the first and second lens data signals DLC, DLC2 shown in Fig. 8(B). After the lens microcomputer 111 starts transmitting the first and second lens data signals DLC, DLC2 in response to the assertion of the transmission request signal RTS by the camera microcomputer 205, the camera microcomputer 205 instructs the lens microcomputer 111 to stop communication during the transmission of frames DL11, DL12. T4w1 indicates a communication stop period during which the camera microcomputer 205 instructs the lens microcomputer 111 to stop communication. The camera microcomputer 205 notifies the lens microcomputer 111 of the instruction by temporarily negating the transmission request signal RTS.

[0106] When the lens microcontroller 111 detects that the transmission request signal RTS has been negated, it stops transmission after completing transmission of frames DL11, DL12 (hereinafter referred to as stop frames) of the first and second lens data signals DLC, DLC2 that were in the middle of transmission at the time of detection.

[0107] When the event requesting stop of communication is no longer present, the camera microcomputer 205 instructs the lens microcomputer 111 to resume communication by reasserting the transmission request signal RTS. In response to the instruction to resume communication, the lens microcomputer 111 resumes transmission of the first and second lens data signals DLC, DLC2 from frames (hereinafter referred to as resume frames) DL13, DL14 next to the stop frame.

[0108] The lens microcomputer 111 continuously transmits restart frames DL13 and DL14, followed by frames DL15 and DL16, and frames DL17 and DL18, in that order. Then, when transmission of frames DL17 and DL18 is completed, a communication stop request event occurs, causing the lens microcomputer 111 to notify the camera microcomputer 205 of communication stop. T4w2 represents a communication stop period during which the lens microcomputer 111 has notified the camera microcomputer 205 of communication stop. The lens microcomputer 111 notifies the camera microcomputer 205 of communication stop by not transmitting the first and second lens data signals DLC and DLC2 even if the transmission request signal RTS is in an asserted state. The camera microcomputer 205 maintains the transmission request signal RTS in an asserted state during the communication stop period T4w2 instructed by the lens microcomputer 111.

[0109] Thereafter, when the communication stop request event in the lens microcomputer 111 disappears, the lens microcomputer 111 resumes transmission of the first and second lens data signals DLC, DLC2 from the next resume frames DL19, DL20 to the camera microcomputer 205. This enables the lens microcomputer 111 to transmit to the camera microcomputer 205 those frames of the first and second lens data signals DLC, DLC2 that were not transmitted due to the transmission stop.

[0110] In this way, in the second communication setting, communication between the camera microcomputer 205 and the lens microcomputer 111 can be stopped by stopping the transmission of the first and second lens data signals DLC, DLC2 from the lens microcomputer 111 to the camera microcomputer 205. This allows a large amount of data to be communicated synchronously from the lens microcomputer 111 to the camera microcomputer 205 at high speed.

[0111] As described above, in this embodiment, in both the first and second communication settings, the suspension and resumption of communication can be instructed from both the camera microcomputer 205 and the lens microcomputer 111. This makes it possible to perform communication control according to the processing load and reception buffer capacity of both the camera microcomputer 205 and the lens microcomputer 111, and large amounts of data can be communicated at high speed without causing communication breakdowns. EXAMPLES

[0112] Next, a second embodiment of the present invention will be described. In this embodiment, a forced stop of continuous transmission (burst communication) of the first and second lens data signals DLC and DLC2 from the lens microcomputer 111 to the camera microcomputer 205 in the second communication setting described in the first embodiment will be described.

[0113] In the second communication setting described in the first embodiment, both the first and second data communication channels are used to transmit the first and second lens data signals DLC, DLC2 from the lens microcomputer 111 to the camera microcomputer 205, thereby enabling high-speed communication of large amounts of data. However, since the second data communication channel, which is originally used for communication of the camera data signal DCL, is used for communication of the second lens data signal DLC2, the camera microcomputer 205 cannot notify the lens microcomputer 111 of instructions by control commands or the like during that communication. Therefore, even if the camera microcomputer 205 recognizes a communication abnormality, particularly during burst communication, the camera microcomputer 205 cannot instruct the lens microcomputer 111 to forcibly stop communication. The communication abnormality referred to here includes data corruption due to static electricity, a sudden removal of the interchangeable lens from the camera body by the user, which causes the communication channel between the camera microcomputer 205 and the lens microcomputer 111 to be cut off, and the like.

[0114] When such a communication abnormality occurs, it is desirable to forcibly stop communication promptly. However, if the second data communication channel is switched to communication of the camera data signal DCL and a forced stop is notified after burst communication from the lens microcomputer 111 to the camera microcomputer 205 is completed in the second communication setting, the stopping of communication will be delayed. In this embodiment, it is possible to forcibly stop communication promptly when such a communication abnormality occurs.

[0115] 10 shows the configuration of a camera system including a camera body 200' and an interchangeable lens 100' in this embodiment. In the camera system of this embodiment, the same components as those in the camera system shown in embodiment 1 (FIG. 1) are denoted by the same reference numerals as in embodiment 1, and a description thereof will be omitted.

[0116] 10, a timer 114 provided in an interchangeable lens 100' measures the time from a time count start command to a time count end command from the lens microcomputer 111. The lens microcomputer 111 outputs a time count start command to the timer 114 in response to the transmission request signal RTS from the camera microcomputer 205 being negated, and outputs a time count end command to the timer 114 in response to the transmission request signal RTS being asserted. This measures the time during which the transmission request signal RTS is negated (hereinafter referred to as the lens side RTS negation time), and information on the lens side RTS negation time is input to the lens microcomputer 111.

[0117] Meanwhile, timer 211 provided in camera body 200' measures the time from a time count start command from camera microcomputer 205. The camera microcomputer 205 negates the request-to-send signal RTS and outputs a time count start command to timer 211. This measures the time during which the camera microcomputer 205 negates the request-to-send signal RTS (hereinafter referred to as camera-side RTS negation time), and information on the camera-side RTS negation time is input to the camera microcomputer 205.

[0118] The process for communication control in this embodiment will be described with reference to the flowchart in FIG. 11. The camera microcomputer 205 and the lens microcomputer 111 execute this process according to a communication control program as a computer program. Here, a case where communication is forcibly stopped when the second communication setting described in the first embodiment is used will be described. However, communication may also be forcibly stopped when the first communication setting is used. The process shown in FIG. 11 starts from a state where the first communication setting is set. In FIG. 11 and the following description, "S" means step.

[0119] In S1101, the camera microcomputer 205 prepares a burst communication request command. The burst communication request command includes information necessary for the lens microcomputer 111 to perform burst communication, such as the communication data amount and bit rate in the burst communication. Then, in S1102, the camera microcomputer 205 transmits the burst communication request command to the lens microcomputer 111 as a camera data signal DLC via the second data communication channel.

[0120] Upon receiving the burst communication request command, the lens microcomputer 111 performs communication preparation in S1201, including generating first and second lens data signals DLC, DLC2 in accordance with information included in the burst communication request command and switching from the first communication setting to the second communication setting. Then, when communication preparation is complete, the lens microcomputer 111 transmits a preparation completion notification to the camera microcomputer 205 as the first camera data signal DLC on the first data communication channel in S1202.

[0121] Upon receiving the preparation completion notification, the camera microcomputer 205 also completes preparation for communication in S1103, and in response thereto asserts a transmission request signal RTS in S1104 to notify the lens microcomputer 111 of a transmission request. In S1203 and S1204, the lens microcomputer 111 that has received the transmission request starts continuous transmission (burst communication) of the first and second lens data signals DLC, DLC2 to the camera microcomputer 205 via the first and second data communication channels, respectively.

[0122] During this burst communication, the camera microcomputer 205 constantly monitors whether a communication error has occurred. Here, it is assumed that in S1105, the camera microcomputer 205 detects that a communication error has occurred while receiving the first lens data signal DLC or the second lens data signal DLC2. The communication error can be detected by determining whether there is a discrepancy between the parity information PA added to each frame and the received data content as shown in FIG. 8(A). In addition, a communication error can also be detected by not being able to normally detect the stop bit ST of each frame. Furthermore, a communication error also includes a case where the interchangeable lens 100 is suddenly removed from the camera body 200 by the user, making communication impossible. The camera microcomputer 205 that detects a communication error proceeds to S1106. The camera microcomputer 205 that does not detect a communication error continues to receive the first and second lens data signals DLC and DLC2.

[0123] In S1106, the camera microcomputer 205 issues a time count start command to the timer 211 to start measuring the camera side RTS negation time. Then, in S1107, the camera microcomputer 205 negates the transmission request signal RTS to instruct the lens microcomputer 111 to stop transmitting the first and second lens data signals DLC and DLC2.

[0124] Upon detecting the negation of the request-to-send signal RTS, the lens microcomputer 111 stops transmitting the first and second lens data signals DLC and DLC2 in S1205. Furthermore, the lens microcomputer 111 issues a time count start command to the timer 114 in S1206 to start measuring the lens side RTS negation time.

[0125] In S1207, the lens microcomputer 111 determines whether the lens side RTS negation time measured by the timer 114 has exceeded a predetermined time A. The predetermined time A may be set in advance as a communication standard between the camera microcomputer 205 and the lens microcomputer 111. The predetermined time A may be notified to the lens microcomputer 111 by transmitting a burst communication request command from the camera microcomputer 205 to the lens microcomputer 111 in S1102 or by a camera data signal DCL transmitted subsequently thereto. A specific example of the predetermined time A will be described later in Example 3. If the camera microcomputer 205 asserts the transmission request signal RTS before the lens side RTS negation time exceeds the predetermined time A, the lens microcomputer 111 resumes transmitting the first and second lens data signals DLC and DLC2.

[0126] When the camera side RTS negation time exceeds the predetermined time A in S1108, the camera microcomputer 205 asserts the transmission request signal RTS in S1109. As a result, the camera microcomputer 205 instructs the lens microcomputer 111 to forcibly stop the transmission of the first and second lens data signals DLC, DLC2. When the lens side RTS negation time exceeds the predetermined time A, the lens microcomputer 111 detects the assertion of the transmission request signal RTS and determines that this is an instruction to forcibly stop the transmission of the first and second lens data signals DLC, DLC2. Then, the lens microcomputer 111 stops the transmission of the first and second lens data signals DLC, DLC2 midway in S1208, and notifies the camera microcomputer 205 of the completion of the forced stop by a notification command transmitted as the first lens data signal DLC in S1209.

[0127] The camera microcomputer 205, which has received notification of the completion of the forced stop from the lens microcomputer 111, stops receiving the first and second lens data signals DLC, DLC2 from the lens microcomputer 111 in S1110. Then, the camera microcomputer 205 switches the second data communication channel from a state in which it can receive the second lens data signal DLC2 to a state in which it can transmit the camera data signal DCL.

[0128] 12A shows signal waveforms when a total of n frames (DL1 to DLn) of the first and second lens data signals DLC, DLC2 are continuously transmitted from the lens microcomputer 111 to the camera microcomputer 205 in the second communication setting with a communication stop period T4w1 in between. In response to the assertion of the transmission request signal RTS by the camera microcomputer 205, the lens microcomputer 111 starts transmitting the first and second lens data signals DLC, DLC2. Thereafter, during the transmission of frames DL11, DL12 from the lens microcomputer 111, the camera microcomputer 205 temporarily negates the transmission request signal RTS, thereby instructing the lens microcomputer 111 to stop communication. When the lens microcomputer 111 detects that the transmission request signal RTS has been negated, it stops transmitting after completing the transmission of the frames DL11, DL12 of the first and second lens data signals DLC, DLC2 that were in the middle of transmission at the time of detection (hereinafter referred to as stop frames). From this point, measurement of the communication suspension period T4w1, i.e., the RTS negation time on the camera side and lens side, begins.

[0129] When the event requesting suspension of communication disappears before the communication suspension period T4w1 exceeds the predetermined time A, the camera microcomputer 205 instructs the lens microcomputer 111 to resume communication by reasserting the transmission request signal RTS. In response to the instruction to resume communication, the lens microcomputer 111 resumes transmission of the first and second lens data signals DLC, DLC2 from the resume frames DL13, DL14 that follow the suspension frame.

[0130] 12B shows waveforms of signals exchanged between the camera microcomputer 205 and the lens microcomputer 111 when the communication suspension period T4w1 described in FIG. 12A exceeds the predetermined time A. When the communication suspension period T4w1 (camera side RTS negation time) exceeds the predetermined time A, the camera microcomputer 205 asserts the transmission request signal RTS that had been negated up until that point, thereby instructing the lens microcomputer 111 to forcibly stop communication. When the communication suspension period T4w1 (lens side RTS negation time) exceeds the predetermined time A, the lens microcomputer 111 detects the assertion of the transmission request signal RTS and determines this as an instruction by the camera microcomputer 205 to forcibly stop communication. In response to this, the lens microcomputer 111 stops transmitting the first and second lens data signals DLC, DLC2 up to the transmission of the stop frames DL11, DL12. Furthermore, the lens microcomputer 111 notifies the camera microcomputer 205 of the forced stop completion (END) by a notification command transmitted as the first lens data signal DLC. The notification of the forced stop completion may be transmitted in one frame or multiple frames. In this way, the lens microcomputer 111 clears the untransmitted frames DL13 to DLn without transmitting them to the camera microcomputer 205.

[0131] In this way, when a communication error occurs during burst communication from the lens microcomputer 111 with the second communication settings, the camera microcomputer 205 can quickly instruct the lens microcomputer 111 to forcibly stop the burst communication.

[0132] In this embodiment, the assertion of the request-to-send signal RTS after the camera-side and lens-side RTS negation times exceed the predetermined time A is described as a simple instruction to forcibly stop burst communication. However, the assertion of this request-to-send signal RTS may also be an instruction to restart burst communication (forcibly stop and start over from the beginning). EXAMPLES

[0133] Next, a third embodiment of the present invention will be described. This embodiment also relates to a forced stop of continuous transmission (burst communication) of the first and second lens data signals DLC, DLC2 from the lens microcomputer 111 to the camera microcomputer 205 in the second communication setting.

[0134] As described in the first embodiment with reference to FIG. 7, the first and second lens data signals DLC, DLC2 stored in the received data buffer 303 in the second communication setting are read out from the received data buffer 303 by the DMA control unit 307 and transferred to the memory 210. This is because the capacity of the received data buffer 303 is insufficient for the amount of data of all frames of the first and second lens data signals DLC, DLC2. However, since the memory 210 is accessed not only by the camera communication unit 208 but also by the signal processing circuit 203 and the like shown in FIG. 1, there is a risk of a waiting time or insufficient processing speed occurring during access contention. At this time, if the camera microcomputer 205 cannot instruct the lens microcomputer 111 to stop the burst communication, there is a risk of the burst communication failing.

[0135] FIG. 13 shows an example of the predetermined time A until the camera microcomputer 205 issues an instruction to forcibly stop the burst communication from the lens microcomputer 111 to the camera microcomputer 205 in this embodiment. The predetermined time A is set according to the amount of data in the burst communication. In this example, if the amount of data in the burst communication is equal to or less than the capacity of the received data buffer (Rx_RAM) 303, the predetermined time A is set to 0 ms. Also, if the amount of data in the burst communication exceeds the capacity of the received data buffer (Rx_RAM) 303, the predetermined time A is set to 20 ms. The predetermined time A can be set arbitrarily according to the capacity of the received data buffer 303 as well as the processing capacity of the camera microcomputer 205. Also, the predetermined time A may be set uniformly regardless of the capacity of the received data buffer 303.

[0136] Table information indicating the predetermined time A relative to the data amount of burst communication may be stored in the internal memory of the camera microcomputer 205, the memory 210, etc. This enables the camera microcomputer 205 to notify the lens microcomputer 111 of the setting of the predetermined time A before the start of burst communication.

[0137] Also, similar table information may be stored in an internal memory or the like of the lens microcomputer 111, and the lens microcomputer 111 may determine the predetermined time A according to the amount of data to be transmitted by burst communication to the camera microcomputer 205 before the start of burst communication. In this case, it is not necessary for the camera microcomputer 205 to notify the lens microcomputer 111 of the setting of the predetermined time A.

[0138] If the predetermined time A is set to 0 ms, when the transmission request signal RTS is asserted from a negated state, the lens microcomputer 111 determines this as an instruction to forcibly stop communication, rather than an instruction to resume communication. On the other hand, if the predetermined time A is set to 20 ms, when the transmission request signal RTS is asserted from a negated state within the predetermined time A, the lens microcomputer 111 determines this as an instruction to resume communication. However, when the transmission request signal RTS is asserted from a negated state after the predetermined time A has elapsed, the lens microcomputer 111 determines this as an instruction to forcibly stop communication.

[0139] According to this embodiment, when the capacity of the received data buffer 303 is sufficient for the amount of data in the burst communication, the time required to forcibly stop the burst communication can be shortened compared to embodiment 2. Therefore, during burst communication with the second communication setting, when the camera microcomputer 205 detects a communication error, it can promptly instruct the lens microcomputer 111 to forcibly stop the burst communication. Therefore, the camera microcomputer 205 can promptly instruct the lens microcomputer 111 to restart the burst communication. EXAMPLES

[0140] A fourth embodiment of the present invention will now be described. In this embodiment, as shown in FIG. 15, a camera body 200" has a memory controller 212 that controls a memory (DDR) 210. Note that in FIG. 15, the camera communication unit 208 included in the camera microcomputer 205 is shown separately from the camera microcomputer 205. The camera body 200" of this embodiment corresponds to the camera body 200' described in the second embodiment to which the memory controller 212 has been added, and the interchangeable lens 100' of this embodiment is the same as that described in the second embodiment.

[0141] The memory controller 212 will now be described. In FIG. 15, a bus IF 506 is a bus interface module that interfaces with a master module that requests memory access inside the chip. The master module refers to the main processing units in the camera body 200'', such as the camera microcomputer 205 and the signal processing circuit 203. The figure shows a configuration that can be connected to two buses of the same or different types.

[0142] The arbiter unit 501 arbitrates and orders the memory access requests to the memory 210 received by the bus IF 506. The queue buffer 502 is used as a buffer that can temporarily store the memory access requests ordered by the arbiter unit 501. The camera microcomputer 205 obtains information on the frequency of memory access requests (hereinafter referred to as memory access frequency) from the memory access requests stored in the queue buffer 502.

[0143] The command issuing unit 503 sequentially retrieves the memory access requests stored in the queue buffer 502, and accesses the memory 210 based on the contents of the requests. The data IF 504 is an interface for reading and writing data from and to the memory 210 in response to the memory access requests issued by the command issuing unit 503.

[0144] For example, when the memory access request selected by the arbiter unit 501 is a command requesting writing of data to the memory 210, the data control unit 505 takes in the write data from the bus interface 1. The data control unit 505 stores the taken in write data until the actual data write timing, and outputs it to the data IF 504. In addition, when the memory access request selected by the arbiter unit 501 is a command requesting reading of data from the memory 210, the data control unit 505 outputs the data read from the memory 210 to the data IF 504.

[0145] In this embodiment, when the camera body 200'' has the above-mentioned memory controller 212, the camera microcomputer 205 will be described as forcibly stopping communication when it detects a communication abnormality during burst communication from the lens microcomputer 111 to the camera microcomputer 205 with the second communication setting. The flowchart in Figure 14 shows the communication control processing between the camera microcomputer 205 and the lens microcomputer 111 in this embodiment. The camera microcomputer 205 and the lens microcomputer 111 perform this processing in accordance with a communication control program as a computer program.

[0146] 14, the camera microcomputer 205 acquires information on the memory access frequency from the memory controller 212 (queue buffer 502). A high memory access frequency means that the memory access request waiting time from the time when the first memory access request is made until the camera communication unit 208 is able to receive burst communication from the lens microcomputer 111 is long.

[0147] Next, in S402, the camera microcomputer 205 uses the memory access frequency acquired in S401 to determine whether or not the shooting mode currently set in the camera body 200'' is a shooting mode in which the memory access frequency of the camera communication unit 208 is high. If so, the process proceeds to S403, and if the shooting mode is a shooting mode in which the memory access frequency is low, the process proceeds to S404.

[0148] In S403, the camera microcomputer 205 sets the predetermined time A, which is the upper limit of the time for negating the transmission request signal RTS and stopping communication (hereinafter referred to as the RTS negation time), to be longer than the time set in S404 described later, in response to a high memory access frequency. In S404, the camera microcomputer 205 sets the predetermined time A to be shorter than the time set in S403 in response to a low memory access frequency. In other words, if the memory access request waiting time is long, the predetermined time A is set to be longer, and if the memory access request waiting time is short, the predetermined time A is set to be shorter.

[0149] Next, in S405, the camera microcomputer 205 transmits a burst communication request command as a camera data signal DLC over the second data communication channel to the lens microcomputer 111. The burst communication request command includes information necessary for the lens microcomputer 111 to perform burst communication, such as the communication data amount and bit rate in burst communication.

[0150] Upon receiving the burst communication request command, the lens microcomputer 111 performs communication preparations in S406, including generating first and second lens data signals DLC, DLC2 in accordance with information included in the burst communication request command and switching from the first communication setting to the second communication setting. Then, when communication preparations are complete, the lens microcomputer 111 transmits a preparation completion notification to the camera microcomputer 205 as the first camera data signal DLC on the first data communication channel.

[0151] Upon receiving the preparation completion notification, the camera microcomputer 205 also completes preparation for communication in S407, and in response asserts a transmission request signal RTS to notify a transmission request to the lens microcomputer 111. Upon receiving the transmission request, the lens microcomputer 111 starts continuous transmission (burst communication) of the first and second lens data signals DLC, DLC2 to the camera microcomputer 205 via the first and second data communication channels.

[0152] During this burst communication, the camera microcomputer 205 constantly monitors whether or not a communication error has occurred. The detection of a communication error is as described in S1105 in the second embodiment. If a communication error is not detected, the camera microcomputer 205 proceeds to S412.

[0153] On the other hand, if a communication error is detected, the camera microcomputer 205 negates the transmission request signal RTS to instruct the lens microcomputer 111 to stop transmitting the first and second lens data signals DLC, DLC2 in S408. Upon detecting the negation of the transmission request signal RTS, the lens microcomputer 111 stops transmitting the first and second lens data signals DLC, DLC2 and gives a time count start command to the timer 114 to start measuring the RTS negation time.

[0154] In S409, the lens microcomputer 111 determines whether the RTS negation time measured by the timer 114 has exceeded a predetermined time A. If the RTS negation time has not exceeded the predetermined time A, the lens microcomputer 111 proceeds to S410 and determines whether the communication request signal RTS has been asserted again by the camera microcomputer 205. If the communication request signal RTS has been asserted, the lens microcomputer 111 resumes transmission of the first and second lens data signals DLC, DLC2 in S411. Then, in S412, the lens microcomputer 111 determines whether transmission of all frames of the first and second lens data signals DLC, DLC2 to be transmitted to the camera microcomputer 205 has been completed, and if transmission has been completed, ends this process. If the communication request signal RTS has not been asserted in S410, the lens microcomputer 111 returns to S409.

[0155] If the RTS negation time measured by the timer 114 in S409 exceeds the predetermined time A, the lens microcomputer 111 proceeds to S413 and determines whether the communication request signal RTS has been asserted again by the camera microcomputer 205. If the communication request signal RTS has been asserted, the lens microcomputer 111 stops transmitting the first and second lens data signals DLC and DLC2 in S414. That is, the lens microcomputer 111 clears the first and second lens data signals DLC and DLC2 without transmitting untransmitted frames to the camera microcomputer 205. The lens microcomputer 111 then notifies the camera microcomputer 205 of the completion of the forced stop by a notification command transmitted as the first lens data signal DLC. The camera microcomputer 205 switches from a state corresponding to the second communication setting to a state corresponding to the first communication setting, and ends this process.

[0156] In this way, if the communication request signal RTS is reasserted before the RTS negation time exceeds the predetermined time A, the lens microcomputer 111 determines this as an instruction to resume burst communication and resumes the stopped burst communication. On the other hand, if the communication request signal RTS is reasserted after the RTS negation time exceeds the predetermined time A, the lens microcomputer 111 determines this as an instruction to forcibly stop burst communication and ends burst communication.

[0157] 16(A) and (B) show signal waveforms when a communication suspension period T4w1 is inserted as an RTS negate time while the first and second lens data signals DLC, DLC2 are continuously transmitted from the lens microcomputer 111 to the camera microcomputer 205 in the second communication setting. The first and second lens data signals DLC, DLC2 originally have a total of n frames (DL1 to DLn), as shown in FIG. 16(B).

[0158] In these figures, the lens microcomputer 111 starts transmitting the first and second lens data signals DLC, DLC2 in response to assertion of a transmission request signal RTS by the camera microcomputer 205. Thereafter, while the lens microcomputer 111 is transmitting frames DL11, DL12, the camera microcomputer 205 temporarily negates the transmission request signal RTS, thereby instructing the lens microcomputer 111 to stop communication. When the lens microcomputer 111 detects that the transmission request signal RTS has been negated, it stops transmission after completing transmission of the frames DL11, DL12 of the first and second lens data signals DLC, DLC2 that were in the middle of transmission at the time of detection (hereinafter referred to as stop frames). From this point, measurement of the communication stop period T4w1, i.e., the RTS negation time, begins.

[0159] Fig. 16(A) shows a case where the predetermined time A is set to a long time because the shooting mode is a shooting mode in which the memory access frequency of the camera communication unit 208 is high. On the other hand, Fig. 16(B) shows a case where the predetermined time A is set to a short time because the shooting mode is a shooting mode in which the memory access frequency of the camera communication unit 208 is low.

[0160] As shown in FIG. 16A, when the camera microcomputer 205 asserts the transmission request signal RTS again after the communication suspension period T4w1 exceeds the predetermined time A, the lens microcomputer 111 judges this as an instruction to forcibly stop communication. In response to this, the lens microcomputer 111 stops transmitting the first and second lens data signals DLC, DLC2 up to the transmission of the stop frames DL11, DL12. Furthermore, the lens microcomputer 111 notifies the camera microcomputer 205 of the completion of the forced stop (END) by a notification command transmitted as the first lens data signal DLC. The notification of the completion of the forced stop may be transmitted in one frame or multiple frames. In this way, the lens microcomputer 111 clears the untransmitted frames DL13 to DLn without transmitting them to the camera microcomputer 205.

[0161] 16B, if the camera microcomputer 205 asserts the transmission request signal RTS again before the communication suspension period T4w1 exceeds the predetermined time A, the lens microcomputer 111 determines this as an instruction to resume communication. In response to this, the lens microcomputer 111 resumes the transmission of the first and second lens data signals DLC, DLC2 from the resume frames DL13, DL14 that follow the suspension frame.

[0162] In this manner, in this embodiment, the upper limit time for communication suspension (predetermined time A) is made variable to accommodate differences in memory access request waiting time that arise due to differences in memory access frequency for the memory 210 that ultimately stores the first and second lens data signals DLC, DLC2. This makes it possible to set an optimal upper limit time for communication suspension according to the storage speed of the first and second lens data signals DLC, DLC2 in the memory 210. Therefore, after the camera body 200'' detects a communication error and suspends communication, it is possible to have the lens microcomputer 111 promptly determine whether to forcibly suspend communication or resume communication.

[0163] In this embodiment, the assertion of the request-to-send signal RTS after the RTS negation time exceeds the predetermined time A is described as simply an instruction to forcibly stop burst communication. However, the assertion of this request-to-send signal RTS may also be an instruction to restart burst communication (forcibly stop and start over from the beginning). Furthermore, when the RTS negation time is about to exceed the predetermined time A, the priority of the access request from the camera microcomputer 205 (camera communication unit 208) to the memory 210 may be increased, so that the burst communication from the lens microcomputer 111 can be completed within the predetermined time A. (Other Examples) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0164] 100 Interchangeable Lenses 111 Lens microcomputer 200 Camera body 205 Camera microcomputer

Claims

1. An accessory device that is removably attached to an imaging device, an accessory control means for controlling communication between the accessory device and the imaging device; The accessory device is characterized in that the accessory control means performs the communication with the imaging device via the second channel connected via the second terminal and the third channel connected via the third terminal without using a clock signal, in response to the signal level of the first channel connected via the first terminal changing from a first signal level to a second signal level and then the signal level of the first channel being maintained at the second signal level.

2. The accessory device according to claim 1, characterized in that the accessory control means transmits multiple frames of accessory data via the second channel as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

3. 3. The accessory device according to claim 1, wherein the accessory control means stops transmitting accessory data in response to a change in the signal level of the first channel from the second signal level to the first signal level.

4. The accessory device according to claim 3, characterized in that, when the signal level of the first channel changes from the second signal level to the first signal level while transmission of accessory data for a certain frame is incomplete, the accessory control means stops transmission of the accessory data to the imaging device after transmission of the frame is completed.

5. The accessory device according to any one of claims 1 to 4, characterized in that the accessory control means transmits accessory data via the second channel and receives camera data via the third channel as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

6. The accessory device according to any one of claims 1 to 5, characterized in that the accessory control means transmits accessory data via the second channel and receives camera data via the third channel in response to the transmission, as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

7. The accessory device according to any one of claims 1 to 6, characterized in that, when the signal level of the first channel is maintained at the second signal level, the accessory control means stops receiving camera data via the third channel in response to the transmission of accessory data via the second channel being stopped.

8. The accessory device according to any one of claims 1 to 7, characterized in that the accessory control means transmits accessory data via the second and third channels as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

9. The accessory device according to claim 8, characterized in that the accessory control means forcibly stops transmission of accessory data via the second and third channels in response to a predetermined time having elapsed after the signal level of the first channel has changed from the second signal level to the first signal level.

10. the accessory control means transmits information indicating a data size of the accessory data; The accessory device described in any one of claims 1 to 9, characterized in that the accessory control means transmits the accessory data of the data size indicated by the information when communicating with the imaging device via the second channel and the third channel in response to the signal level of the first channel being maintained at the second signal level after the signal level of the first channel changes from the first signal level to the second signal level.

11. The accessory device according to any one of claims 1 to 10, characterized in that the accessory control means has a first mode and a second mode in which the number of frames of data that can be communicated after the signal level of the first channel changes from the first signal level to the second signal level is different.

12. The accessory device of claim 11, characterized in that in the first mode, the accessory control means transmits multiple frames of accessory data via the second channel as the communication performed in response to the signal level of the first channel being maintained at the second signal level, and in the second mode, the accessory control means transmits one frame of accessory data via the second channel as the communication performed in response to the signal level of the first channel changing from the first signal level to the second signal level.

13. 13. The accessory device according to claim 11, wherein the accessory control means transmits information indicating a data size of the accessory data in the second mode.

14. 14. The accessory device according to claim 10, wherein the information indicating a data size of the accessory data indicates a number of frames to be transmitted as the data size.

15. The accessory device according to claim 10, characterized in that, when transmission of accessory data of a data size indicated by the information has not been completed, the accessory control means stops transmitting the accessory data in response to a change in the signal level of the first channel from the second signal level to the first signal level, and resumes the transmission in response to a change in the signal level of the first channel from the first signal level to the second signal level after the transmission has been stopped.

16. the accessory control means transmits information indicating a data size of the accessory data; The accessory device according to any one of claims 1 to 8, characterized in that when the signal level of the first channel changes from the second signal level to the first signal level while transmission of accessory data of a certain frame is incomplete, the accessory control means stops transmitting the accessory data after transmission of the frame is completed, even if the data size of the transmitted accessory data is smaller than the data size indicated by the information.

17. The accessory control means includes: after a signal level of the first channel changes from the first signal level to the second signal level, accessory data is transmitted via the second channel in response to the signal level of the first channel being maintained at the second signal level; The accessory device of claim 1, further comprising: a control unit that controls the camera data transmitted from the imaging device in response to the transmission of the accessory data via the second channel to be received via the third channel in response to the signal level of the first channel being maintained at the second signal level after the signal level of the first channel has changed from the first signal level to the second signal level.

18. 17. The accessory device according to claim 2, 4, 11, 12, 14 or 16, wherein one frame has a start bit, 8 bits of data and a stop bit.

19. The accessory device according to any one of claims 1 to 18, wherein the accessory device is a lens device.

20. 20. The accessory device according to claim 1, wherein the first terminal, the second terminal and the third terminal are different terminals.

21. An imaging device to which an accessory device is removably attached, a camera control means for controlling communication between the imaging device and the accessory device; The imaging device is characterized in that the camera control means performs the communication with the accessory device via the second channel connected via the second terminal and the third channel connected via the third terminal without using a clock signal, in response to the signal level of the first channel connected via the first terminal changing from the first signal level to the second signal level and then the signal level of the first channel being maintained at the second signal level.

22. The imaging device according to claim 21, characterized in that the camera control means receives multiple frames of accessory data via the second channel as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

23. 23. The imaging device according to claim 21, wherein the camera control means stops receiving accessory data in response to a change in the signal level of the first channel from the second signal level to the first signal level.

24. The imaging device described in any one of claims 21 to 23, characterized in that when the signal level of the first channel changes from the second signal level to the first signal level while reception of accessory data for a certain frame is incomplete, the camera control means stops receiving the accessory data after reception of the frame is completed.

25. The imaging device according to any one of claims 21 to 24, characterized in that the camera control means receives accessory data via the second channel and transmits camera data via the third channel as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

26. The imaging device described in any one of claims 21 to 25, characterized in that the camera control means receives accessory data via the second channel and transmits camera data via the third channel in response to the reception, as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

27. 27. The imaging device according to claim 21, wherein the camera control means stops transmitting camera data via the third channel in response to stopping reception of accessory data via the second channel when the signal level of the first channel is maintained at the second signal level.

28. The imaging device according to any one of claims 21 to 27, characterized in that the camera control means receives accessory data via the second and third channels as the communication performed in response to the signal level of the first channel being maintained at the second signal level.

29. The imaging device according to claim 28, characterized in that the camera control means forcibly stops reception of accessory data via the second and third channels in response to a predetermined time having elapsed after the signal level of the first channel has changed from the second signal level to the first signal level.

30. The camera control means receives information indicating a data size of the accessory data, The imaging device described in any one of claims 21 to 29, characterized in that the camera control means receives the accessory data of the data size indicated by the information when communicating with the accessory device via the second channel and the third channel in response to the signal level of the first channel changing from the first signal level to the second signal level and then the signal level of the first channel being maintained at the second signal level.

31. 31. The imaging device according to claim 22, wherein the camera control means has a first mode and a second mode in which the number of frames of data that can be communicated after the signal level of the first channel changes from the first signal level to the second signal level is different.

32. The imaging device of claim 31, characterized in that in the first mode, the camera control means receives multiple frames of accessory data via the second channel as the communication performed in response to the signal level of the first channel being maintained at the second signal level, and in the second mode, the camera control means receives one frame of accessory data via the second channel as the communication performed in response to the signal level of the first channel changing from the first signal level to the second signal level.

33. 33. The imaging apparatus according to claim 31, wherein the camera control means transmits information indicating a data size of the accessory data in the second mode.

34. 34. The imaging device according to claim 30, wherein the information indicating the data size of the accessory data indicates the number of frames to be received as the data size.

35. The imaging device described in claim 30, characterized in that, when reception of accessory data of the data size indicated by the information has not been completed, the camera control means stops receiving the accessory data in response to a change in the signal level of the first channel from the second signal level to the first signal level, and resumes the reception in response to a change in the signal level of the first channel from the first signal level to the second signal level after the reception has stopped.

36. The camera control means receives information indicating a data size of the accessory data, The imaging device described in any one of claims 21 to 28, characterized in that when the signal level of the first channel changes from the second signal level to the first signal level while reception of accessory data for a certain frame is incomplete, the camera control means stops receiving the accessory data after reception of the frame is completed, even if the data size of the received accessory data is smaller than the data size indicated by the information.

37. The camera control means receiving accessory data via the second channel in response to a signal level of the first channel being maintained at the second signal level after the signal level of the first channel has changed from the first signal level to the second signal level; The imaging device according to claim 21, characterized in that after the signal level of the first channel changes from the first signal level to the second signal level, in response to the signal level of the first channel being maintained at the second signal level, control is performed so that camera data transmitted in response to reception of the accessory data via the second channel is transmitted via the third channel.

38. 37. The imaging device according to claim 22, 24, 31, 32, 34, or 36, wherein one frame has a start bit, 8 bits of data, and a stop bit.

39. 39. The imaging device according to claim 21, wherein the accessory device is a lens device.

40. 40. The imaging device according to claim 21, wherein the first terminal, the second terminal and the third terminal are different terminals.

41. 1. A control method for controlling communication between an accessory device that is detachably attached to an imaging device and the imaging device, comprising: A control method comprising a step of performing the communication with the imaging device via a second channel connected via a second terminal and a third channel connected via a third terminal without using a clock signal, in response to the signal level of a first channel connected via a first terminal changing from a first signal level to a second signal level and then the signal level of the first channel being maintained at the second signal level.

42. 1. A control method for controlling communication between an imaging device to which an accessory device is removably attached, the imaging device and the accessory device, comprising: A control method comprising a step of performing the communication with the accessory device via a second channel connected via a second terminal and a third channel connected via a third terminal without using a clock signal, in response to the signal level of a first channel connected via a first terminal changing from a first signal level to a second signal level and then the signal level of the first channel being maintained at the second signal level.

43. A storage medium storing a program for causing a computer to execute a control method for controlling communication between an accessory device that is detachably attached to an imaging device and the imaging device, the storage medium comprising: The control method includes: A computer-readable storage medium comprising a step of performing the communication with the imaging device via a second channel connected via a second terminal and a third channel connected via a third terminal without using a clock signal, in response to the signal level of a first channel connected via a first terminal changing from a first signal level to a second signal level and the signal level of the first channel being maintained at the second signal level.

44. A storage medium storing a program for causing a computer to execute a control method for controlling communication between an imaging device to which an accessory device is detachably attached and the imaging device, the storage medium comprising: The control method includes: A computer-readable storage medium, comprising a step of performing the communication with the accessory device via a second channel connected via a second terminal and a third channel connected via a third terminal without using a clock signal, in response to the signal level of a first channel connected via a first terminal changing from a first signal level to a second signal level and the signal level of the first channel being maintained at the second signal level.

45. A lens device that is removably attached to an imaging device, an accessory control unit for controlling communication between the lens device and the imaging device; The lens device is characterized in that the accessory control means performs the communication with the imaging device via the second channel and the third channel without using a clock signal in response to the signal level of the first channel changing from a first signal level to a second signal level and then the signal level of the first channel being maintained at the second signal level.

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