Vehicle display device

Abstract

Impedance matching is performed at appropriate intervals to suppress the reduction in effective communication speed between the control unit and RAM. [Solution] A vehicle display device 10 comprises a display unit 13, a storage unit 14 including RAM 142 and ROM 141, and a control unit 12 that controls the display unit 13 using the storage unit 14. The RAM 142 has an impedance matching function that performs impedance matching in response to instructions from the control unit 12, the ROM 141 stores a plurality of specified times t1, t2 that define the execution period of impedance matching, the control unit 12 selects one of the plurality of specified times t1, t2 stored in the ROM 141 and instructs the RAM 142 to perform impedance matching at a period determined by the selected specified times t1, t2, and the selection conditions for the specified times t1, t2 by the control unit 12 include the elapsed time since the vehicle display device 10 was started.

Description

Technical Field

[0001] The present disclosure relates to a display device for a vehicle.

Background Art

[0002] In order to prevent communication failures due to impedance mismatches between a control unit and a RAM (e.g., DDR3 - SDRAM), a RAM capable of performing impedance matching (e.g., ZQ calibration) is known (see, for example, Patent Document 1). Since impedance varies depending on the temperature of the semiconductor, it is recommended to perform impedance matching of the RAM at a predetermined period during the operation of the device. Also, immediately after the device is started and power is supplied to the semiconductor, the amount of change in impedance becomes large due to self - heating, so it is preferable to perform impedance matching of the RAM at a period that can follow the amount of change.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since impedance matching of the RAM uses the internal circuit of the RAM, access to the RAM is prohibited during impedance matching, which may reduce the effective communication speed between the control unit and the RAM.

[0005] Therefore, an object of the present disclosure is to provide a display device for a vehicle that can perform impedance matching at an appropriate period and suppress a decrease in the effective communication speed between the control unit and the RAM.

Means for Solving the Problems

[0006] In one aspect, the following solution means is provided. Display unit and A storage unit including RAM and ROM, A vehicle display device comprising a control unit that controls the display unit using the storage unit, The RAM is equipped with an impedance matching function that performs impedance matching in response to instructions from the control unit. The ROM stores a plurality of specified times that define the execution period of the impedance matching, The control unit selects one of the multiple predetermined time periods stored in the ROM, and instructs the RAM to perform the impedance matching at a cycle determined by the selected predetermined time period. The selection criteria for the specified time by the control unit include the elapsed time since the vehicle display device was activated. [Effects of the Invention]

[0007] According to this disclosure, impedance matching can be performed at appropriate intervals, thereby suppressing a decrease in the effective communication speed between the control unit and the RAM. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram showing the configuration of a vehicle display device. [Figure 2] This flowchart shows the processing procedure for impedance matching instructions according to the first embodiment. [Figure 3] This flowchart shows the processing procedure for impedance matching instructions according to the second embodiment. [Modes for carrying out the invention]

[0009] The following describes each embodiment in detail with reference to the attached drawings.

[0010] (First embodiment) Figure 1 is a block diagram showing the configuration of the vehicle display device 10. As shown in Figure 1, the vehicle display device 10 of this embodiment includes a power supply circuit 11, a control unit 12, a display unit 13, and a storage unit 14.

[0011] The power supply circuit 11 transforms the power supplied from the vehicle's battery B as needed and supplies it to each part of the vehicle's display device 10.

[0012] The control unit 12 is a computing device such as a microcontroller, and it controls the display unit 13 using the storage unit 14.

[0013] The display unit 13 is configured using a display panel such as a TFT (Thin Film Transistor) liquid crystal display and displays vehicle content such as vehicle information and navigation information.

[0014] The memory unit 14 includes a ROM (Read Only Memory) 141 and a RAM (Random Access Memory) 142.

[0015] ROM 141 stores (saves) programs and data for the control unit 12 to control the display unit 13. The programs and data stored in ROM 141 include programs and setting information (such as specified times t1, t2, predetermined time T, and predetermined amounts A1, A2) for instructing the execution of impedance matching, which will be described later. Note that the programs and setting information for instructing the execution of impedance matching may be stored in a ROM built into the control unit 12, or they may be stored in a distributed manner across multiple ROMs.

[0016] RAM142 is, for example, DDR3-SDRAM, and is used by the control unit 12 as a working memory area. While communication between the control unit 12 and RAM142 can be sped up by lowering the amplitude voltage, this has the disadvantage of making it more susceptible to noise superimposed on the signal line. Therefore, if there is an impedance mismatch in the communication path, the reflected wave of the communication signal may be superimposed on the communication waveform, potentially preventing communication between the control unit 12 and RAM142.

[0017] As a means to prevent such impedance mismatches, the ZQ calibration function implemented in DDR3-SDRAM is known. ZQ calibration is a function in which the DDR3-SDRAM performs impedance matching according to an instruction from the control unit 12.

[0018] Since the impedance changes depending on the temperature of the semiconductor, it is recommended to perform impedance matching of the RAM 142 at a predetermined cycle during the operation of the vehicle display device 10. Also, immediately after the vehicle display device 10 is started and power is supplied to the semiconductor, the amount of change in impedance increases due to self-heating, so it is preferable to perform impedance matching of the RAM 142 at a cycle that can follow the amount of change. However, since impedance matching of the RAM 142 uses the internal circuit of the RAM 142, access to the RAM 142 is prohibited during impedance matching, which may reduce the effective communication speed between the control unit 12 and the RAM 142.

[0019] Therefore, the ROM 141 of the present embodiment stores a plurality of specified times t1, t2 (t1 < t2) that define the execution cycle of impedance matching. Further, the control unit 12 selects one of the plurality of specified times t1, t2 stored in the ROM 141, and instructs the RAM 142 to execute impedance matching at a cycle according to the selected specified times t1, t2. That is, the control unit 12 executes impedance matching of the RAM 142 at an appropriate cycle, and suppresses a decrease in the effective communication speed between the control unit 12 and the RAM 142. In the present embodiment, two specified times t1, t2 are provided, but three or more may be provided.

[0020] The selection conditions for the specified times t1 and t2 by the control unit 12 include the elapsed time since the vehicle display device 10 was activated. Usually, within a predetermined time T after the vehicle display device 10 is activated, due to the heat generation of the semiconductor and the operation of the air conditioning equipment in the vehicle interior by the driver, the temperature inside the vehicle display device 10 changes significantly, so the impedance change between the control unit 12 and the RAM 142 also becomes large. In such a situation, the control unit 12 selects the specified time t1 and instructs the RAM 142 to perform impedance matching at a cycle based on the specified time t1. Thereby, communication failure between the control unit 12 and the RAM 142 due to impedance mismatch is prevented.

[0021] On the other hand, when a certain amount of time (for example, the predetermined time T) has elapsed since startup, the temperature change inside the vehicle display device 10 decreases, and the impedance change also decreases. Therefore, when the elapsed time since startup becomes longer than the predetermined time T, the control unit 12 selects a specified time t2 that is longer than the specified time t1 applied at startup and instructs the RAM 142 to perform impedance matching at a cycle based on the specified time t2. Thereby, it becomes possible to reduce the number of times of performing impedance matching and suppress a decrease in the effective communication speed between the control unit 12 and the RAM 142.

[0022] Note that the predetermined time T is affected by factors such as the heat generation amount, volume capacity, and mounting position of the vehicle display device 10 itself and cannot be represented by a unique numerical value. Therefore, it is desirable to set the best value for each product.

[0023] Next, the specific processing procedure of the control unit 12 for realizing the impedance matching instruction as described above will be described with reference to FIG. 2.

[0024] FIG. 2 is a flowchart showing the processing procedure of the impedance matching instruction according to the first embodiment. As shown in Figure 2, when the vehicle display device 10 is started up, the control unit 12 starts monitoring the elapsed time since startup (S101) and determines whether the elapsed time since startup is within a predetermined time T (S102). If the determination result of step S102 is YES, the control unit 12 sets the time measurement counter to 0 (S103) and then repeats the delay process (WAIT) until the counter value reaches t1 (S104: YES) (S105). If the control unit 12 determines that the counter value has exceeded t1 (S104: NO), it instructs the RAM 142 to perform impedance matching (S106) and returns to step S102. In other words, if the elapsed time since startup is within a predetermined time T, the control unit 12 instructs the RAM 142 to perform impedance matching at a cycle of a predetermined time t1.

[0025] If the control unit 12 determines that the elapsed time since startup has exceeded a predetermined time T (S102: NO), it sets the time measurement counter to 0 (S107), and then repeats the delay process (WAIT) until the counter value reaches t2 (S108: YES) (S109). If the control unit 12 determines that the counter value has exceeded t2 (S108: NO), it instructs the RAM 142 to perform impedance matching (S110), and returns to step S107. In other words, if the elapsed time since startup exceeds a predetermined time T, the control unit 12 instructs the RAM 142 to perform impedance matching with a period of a predetermined time t2 that is longer than the predetermined time t1 applied at startup.

[0026] (Second example) Next, the vehicle display device 10 of the second embodiment will be described with reference to Figures 1 and 3. However, for components common to the first embodiment, the same reference numerals as in the first embodiment will be used, and the description of the first embodiment may be referred to.

[0027] The vehicle display device 10 of the second embodiment includes a temperature sensor S for detecting the temperature of the vehicle display device 10. The temperature sensor S may be a temperature sensor for determining brightness adjustment that is incorporated into the display unit 13, or a temperature sensor that is provided inside the control unit 12.

[0028] In the vehicle display device 10 of the second embodiment, the detection temperature of the temperature sensor S is included in the selection conditions of the prescribed times t1 and t2 by the control unit 12. For example, when the temperature change per unit time becomes larger than a predetermined amount (for example, A2), the control unit 12 makes the execution period of impedance matching smaller than the current period (for example, the period based on the prescribed time t2) (for example, selects the prescribed time t1). Further, when the temperature change per unit time becomes smaller than a predetermined amount (for example, A1 (A1 < A2)), the control unit 12 makes the execution period of impedance matching larger than the current period (for example, the period based on the prescribed time t1) (for example, selects the prescribed time t2). By doing so, it becomes possible to appropriately adjust the execution period of impedance matching in consideration of not only the elapsed time since startup but also the temperature change of the vehicle display device 10.

[0029] For example, even after a lapse of a predetermined time T since startup, the internal temperature of the vehicle display device 10 may change significantly due to changes in the outside air temperature of the vehicle or the operation of the air conditioning temperature in the vehicle cabin by the driver. In this case, the impedance changes rapidly with the change in the internal temperature of the vehicle display device 10, and there is a possibility that the establishment of communication between the control unit 12 and the RAM 142 deteriorates.

[0030] Therefore, when the control unit 12 of the second embodiment reads the value of the temperature sensor S arranged in the vehicle display device 10 and determines that the amount of temperature change per unit time exceeds a predetermined amount A2, it switches the prescribed time from t2 to t1 and reduces the execution period of impedance matching. Thereby, even after a lapse of a predetermined time T since startup, it is possible to avoid impedance mismatch due to a rapid temperature change and maintain the establishment of communication between the control unit 12 and the RAM 142.

[0031] Furthermore, in the second embodiment, the control unit 12 switches the specified time from t2 to t1 based on the amount of temperature change per unit time, and after a predetermined time T has elapsed, it determines whether the amount of temperature change per unit time has fallen within a predetermined amount A1. If the control unit 12 determines that the amount of temperature change per unit time has fallen within a predetermined amount A1, it switches the specified time from t1 to t2 and increases the impedance matching execution cycle again. This reduces the number of impedance matching executions and suppresses the decrease in the effective communication speed between the control unit 12 and the RAM 142.

[0032] Next, the specific processing procedure of the control unit 12 that realizes the impedance matching instruction of the second embodiment will be described with reference to Figure 3.

[0033] Figure 3 is a flowchart showing the processing procedure for impedance matching instructions according to the second embodiment. As shown in Figure 3, when the vehicle display device 10 is started up, the control unit 12 starts monitoring the elapsed time since startup (S201) and determines whether the elapsed time since startup is within a predetermined time T (S202). If the determination result of step S202 is YES, the control unit 12 sets the time measurement counter to 0 (S203) and then repeats the delay process (WAIT) until the counter value reaches t1 (S204: YES) (S205). If the control unit 12 determines that the counter value has exceeded t1 (S204: NO), it instructs the RAM 142 to perform impedance matching (S206) and returns to step S202. In other words, if the elapsed time since startup is within a predetermined time T, the control unit 12 instructs the RAM 142 to perform impedance matching at a cycle of a predetermined time t1.

[0034] If the control unit 12 determines that the elapsed time since startup has exceeded a predetermined time T (S202: NO), it determines whether the temperature change per unit time is greater than a predetermined amount A1 (S207). If the result of this determination is YES, the control unit 12 proceeds to step S203 and again instructs the RAM 142 to perform impedance matching with a period of predetermined time t1.

[0035] If the result of the determination in step S207 is NO, the control unit 12 determines whether the temperature change per unit time is less than a predetermined amount A2 (A2 > A1) (S208). If the result of this determination is YES, the control unit 12 sets the time measurement counter to 0 (S209) and then repeats the delay process (WAIT) until the counter value reaches t2 (S210: YES) (S211). If the control unit 12 determines that the counter value has exceeded t2 (S210: NO), it instructs the RAM 142 to perform impedance matching (S212) and returns to step S208. In other words, if the elapsed time since startup exceeds a predetermined time T and the temperature change per unit time is less than a predetermined amount A2, the control unit 12 instructs the RAM 142 to perform impedance matching with a period of a predetermined time t2 that is longer than the predetermined time t1 applied at startup.

[0036] If the result of the determination in step S208 is NO, the control unit 12 resets the elapsed time since startup (S213) and returns to step S202. In other words, even after a predetermined time T has elapsed since startup, if the temperature change per unit time exceeds a predetermined amount A2, the control unit 12 switches the predetermined time from t2 to t1, reducing the execution period of impedance matching.

[0037] Although each embodiment has been described in detail above, the invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope described in the claims. Furthermore, it is possible to combine all or more of the components of the embodiments described above. [Explanation of symbols]

[0038] 10 Vehicle display devices 11 Power circuit 12 Control Unit 13 Display section 14 Storage section 141 ROM 142 RAM

Claims

1. Display unit and A storage unit including RAM and ROM, A vehicle display device comprising a control unit that controls the display unit using the storage unit, The RAM is equipped with an impedance matching function that performs impedance matching in response to instructions from the control unit, The ROM stores a plurality of specified times that define the execution period of the impedance matching, The control unit selects one of the multiple predetermined time periods stored in the ROM, and instructs the RAM to perform the impedance matching at a cycle determined by the selected predetermined time period. A vehicle display device in which the selection condition for the specified time by the control unit includes the elapsed time since the vehicle display device was activated.

2. The vehicle display device according to claim 1, wherein the control unit increases the execution cycle compared to the startup cycle when the elapsed time exceeds a predetermined time.

3. It is further equipped with a temperature sensor that detects temperature, The vehicle display device according to claim 1, wherein the selection condition for the specified time by the control unit includes the temperature detected by the temperature sensor.

4. The vehicle display device according to claim 3, wherein the control unit reduces the execution period to a smaller period than the current period when the temperature change per unit time becomes greater than a predetermined amount.

5. The vehicle display device according to claim 3, wherein the control unit increases the execution period from the current period when the temperature change per unit time becomes smaller than a predetermined amount.

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