Processing hart signals

Abstract

The invention relates to a method for processing HART signals by means of a HART modem unit (2), the method comprising the following steps: obtaining an FSK-modulated signal via a HART interface (4), demodulating the FSK-modulated signal into a digital data sequence, extracting a HART data frame from the digital data sequence, comparing a first address, encoded in an address field of the HART data frame, with a second address and, if the first address matches the second address, outputting an addressing notification to a processor (3). Further aspects of the invention propose a HART modem unit (2), a computer program product for processing HART signals, a method for processing and obtaining HART signals by means of a HART modem unit (2), and a processor (3) and a field device (1).

Description

[0001] VEG745 1

[0002] Processing of HART signals

[0003] The invention relates to a method for processing HART signals, a HART modem unit, a computer program product for processing HART signals, a method for processing and receiving HART signals, and a field device.

[0004] In process automation technology, field devices are frequently used to detect and / or influence process variables. Examples of such field devices include level gauges, limit level gauges, and pressure gauges with sensors that detect the corresponding process variables: level, limit level, or pressure. These field devices are often connected to higher-level units, such as control systems. These higher-level units are used for process control, process visualization, and / or process monitoring. Field devices known from the prior art typically consist of a housing, a sensor, and a control unit or data processing device located within the housing.

[0005] According to current technology, energy and / or signal transmission between field devices and higher-level units often follows the established 4 mA to 20 mA standard, which uses a 4 mA to 20 mA current loop or a two-wire connection between the field device and the higher-level unit. Signals are transmitted by changing the current. This is an analog approach to data transmission. In addition, the HART protocol exists as a method for digital communication that builds upon the 4 mA to 20 mA technology.

[0006] According to the HART (Highway Addressable Remote Transducer) protocol, digital data is modulated onto the 4 to 20 mA signal. This is done at the physical layer using Frequency Shift Keying (FSK). Different frequencies are assigned to each logical one and logical zero. The amplitude of the 4 to 20 mA signal is modulated with different frequencies, which are evaluated during demodulation to obtain a digital data sequence. HART bytes are encoded in the digital data sequence according to UART. The HART protocol specifies formats for HART-VEG745 2.

[0007] Data frames, also known as telegrams, contain, for example, an address field and a data field. The HART protocol operates according to the master-slave principle. A master device sends a master command, which the slave device then responds to. For example, a control center could send a master command to a field device to retrieve data, which would then respond with a measurement from the control center.

[0008] A fieldbus allows numerous terminal devices to be connected to a control center. According to the prior art, a field device can be equipped with a HART modem unit. The HART modem unit is capable of FSK modulation and demodulation. Upon receiving a HART signal, the HART modem unit forwards a demodulated digital data sequence to a processor in the field device. The processor then handles the processing of the digital data sequence at the protocol level. The processor may also need to process HART data frames that are not addressed to the field device. Against this background, the invention aims to provide a method for processing HART signals that can perform preprocessing of HART signals to relieve the associated processor in a field device.Further objects of the invention are to propose a HART modem unit, a computer program product for processing HART signals, a method for processing and receiving HART signals, and a field device, which have a corresponding preprocessing of HART signals as their subject.

[0009] The problems are solved by the method for processing HART signals according to claim 1, the HART modem unit according to claim 9, the computer program product for processing HART signals according to claim 10, the method for processing and receiving HART signals according to claim 11, and the field device according to claim 15. The dependent claims relate to optional embodiments of the invention.

[0010] It is pointed out that the features listed in the independent and dependent claims can be combined with one another in any way, insofar as this is technically reasonable. This also applies across the boundaries of the claim categories and even if a VEG745 3

[0011] The patent claim is not dependent on any other patent claim. The description further characterizes and specifies the invention, particularly in connection with the figures. If elements in the patent claims or the description are designated with numerical terms such as "first," "second," etc., these numerical terms serve only to distinguish the elements but do not make any statement about an order, a total number, or other properties of the elements, unless explicitly stated otherwise.

[0012] According to a first aspect of the invention, a method for processing HART signals by a HART modem unit is proposed. The method comprises the following steps: receiving an FSK-modulated signal via a HART interface, demodulating the FSK-modulated signal into a digital data sequence, extracting a HART data frame from the digital data sequence, comparing a first address encoded in an address field of the HART data frame with a second address, and, if the first address matches the second address, outputting an addressing notification to a processor.

[0013] The preceding steps are preferably performed by a HART modem unit. According to the invention, the FSK-modulated HART signal can first be demodulated. For example, a HART signal with frequencies of 2200 Hz or 1200 Hz can be modulated onto a current to represent a logical zero or a logical one, respectively. The amplitude of the current preferably changes by a small value, for example + / - 0.5 mA, at the corresponding frequency. The digital data sequence is understood to be a sequence of logical ones and zeros.

[0014] After demodulation, the digital data sequence is not immediately forwarded to the processor. Instead, a HART data frame is extracted from the digital data sequence by the HART modem unit. The digital data sequence is preferably processed such that a HART data frame within the digital data sequence is recognized and / or the contents of data fields within the HART data frame are determined. The extraction of the HART data frame can advantageously include at least one of the following steps: reading bytes from the digital data stream, preferably based on the UART protocol; error detection; and identification of the HART data frame and / or individual data fields within the HART data frame.

[0015] Preferably, the first address is read from an address field of the HART data frame. This first address is preferably a destination address, indicating the receiver to which the HART data frame is directed. The second address is preferably pre-stored in the HART modem unit, for example, in a memory location within the HART modem unit. The processor, or a unit to which the processor belongs (e.g., a field device), can then be addressed using this second address.

[0016] Since the addressing notification is only sent to the processor if the first address matches the second address, the processor is only informed of the HART data frame input if the processor, or the unit associated with it, is actually addressed by the HART data frame. Thus, according to the invention, the processor is not unnecessarily informed of the HART data frame input. A processor that is, for example, in a sleep mode, is therefore not notified and does not have to switch to an operating mode unnecessarily. A further advantage of the method according to the invention is that the extraction of the HART data frame from the digital data sequence is already performed by the HART modem unit. Therefore, the HART data frame extraction does not have to be performed by the processor. Consequently, the processor can use its computing resources for other purposes.Advantageously, the addressing notification is issued as soon as a header of the HART data frame has been completely extracted and / or evaluated. The HART data frame header is preferably formed by a section of the HART data frame containing a preamble, a start byte (SD), an address (AD), a HART command byte (CD), and a byte counter (BC). This allows the addressing notification to be issued early, even before the HART data frame has been completely extracted and / or evaluated.

[0017] The addressing notification can be a notification of any form that is sent to the processor. Preferably, it is a notification that is transmitted to the processor via one or more data lines. Thus, according to the invention, it is possible for the HART modem unit to communicate with the processor via a data bus. The data bus can preferably be a data bus for the VEG745 5

[0018] Communication between digital circuits can be handled, for example, via an on-chip bus or a system bus. For example, the SPI bus (Serial Peripheral Interface) can be used.

[0019] It is advantageous if the addressing notification is an interrupt. An interrupt is preferably suitable for interrupting an existing program execution by the processor and / or notifying the processor of an exception request. Advantageously, the interrupt can trigger an interrupt routine in the processor so that the processor can react to the receipt of the HART signal by the HART modem unit. According to the invention, the interrupt routine can be configured such that the processor switches from an idle mode to an operating mode and / or that the processor prepares to receive data from the HART data frame and / or that the processor sends a request to the HART modem unit, causing the HART modem unit to send data from the HART data frame to the processor, and / or that the processor receives the data from the HART data frame.According to the invention, the interrupt can be transmitted or sent to the processor via at least one data line or data bus. Alternatively, the interrupt is transmitted or sent to the processor via an interrupt line. This can be an interrupt line of a system bus via which the HART modem unit is coupled to the processor.

[0020] Preferably, the HART modem unit performs at least one function of the data link layer. Alternatively or additionally to the address check described above, error checking is preferably performed during the demodulation of the FSK-modulated signal and / or during the extraction of the HART data frame. If an error is detected during error checking, an error message is preferably sent to the processor. According to the invention, the error message can be transmitted to the processor via at least one data line or a data bus. Preferably, the HART modem unit performs the error checking. This can include checking for transmission errors or other errors. In case of an error, the processor is preferably notified. According to the invention, this can be done by means of an interrupt. It is advantageous if the error message includes information about the type of error.

[0021] According to the invention, the error can be a parity error, a framing error, or a gap error detected during the extraction of the HART data frame from the digital data sequence. A parity error is an error that occurs when a data error exists according to one or more parity bits. For example, parity bits can be checked at the UART encoding level. Furthermore, the HART data frame can contain a parity field, which can be used to check the integrity of data within the HART data frame. According to the invention, an error notification can be issued if a data error is detected based on the parity bit and / or the parity byte.

[0022] A framing error occurs, in particular, if a HART data frame cannot be read completely or if reading of the HART data frame does not begin at the correct position. Specifically, a framing error can be triggered if, during the decoding of byte data from the digital data sequence according to UART, no stop bit is detected, or if the stop bit is not detected at an expected position or within a predefined time period. A gap error occurs when an impermissible delay occurs during data transmission. According to an advantageous embodiment of the invention, a notification of a gap error is triggered when there is a gap of more than 11 bits between two UART characters.

[0023] The output of the addressing notification to the processor is preferably not performed if the error is detected and the HART data frame does not require a response from the processor. In this case, only the error notification is output to the processor. Cases may occur where a response from the processor is required even though the error exists. In this case, the addressing notification is output despite the error. Whether the HART data frame requires a response despite the error may depend, for example, on whether a specific HART command byte is present in the HART data frame, whether certain data is contained in HART data bytes of the HART data frame, and / or on some other condition. A check to see if such a condition is met is preferably performed by the HART modem unit. According to other embodiments, VEG745 7

[0024] Is it possible for the addressing notification to always be sent to the processor, even in the event of an error? In another embodiment, the addressing notification is never sent to the processor if an error is detected. Furthermore, variations of the method are possible whereby, if an error is detected, neither the addressing notification nor the error notification is sent to the processor. Thus, the processor is not notified if data received from the HART modem unit is not addressed to the processor and / or is erroneous.

[0025] According to the invention, the method can further include outputting at least one frame byte from the HART data frame to the processor. This allows data from the HART data frame to be transmitted to the processor via the HART modem unit. According to the invention, the frame bytes can be any bytes from the HART data frame, which may contain, for example, a preamble, a start byte, an address, a HART command byte, a byte counter, two status bytes, data bytes, a parity byte, and optionally other byte fields. The processor can then process the data further. According to the invention, the at least one frame byte can be output to the processor automatically, for example, immediately after the addressing notification is issued or within a specific time period after the addressing notification is issued.It is preferable not to output all frame bytes from the HART data frame to the processor. It is advantageous to output only the contents of specific data fields from the HART data frame to the processor.

[0026] The output of the at least one frame byte preferably occurs via the same mechanism or data line as the output of the addressing message. However, it is also possible for the output of the at least one frame byte to the processor to occur via a different communication path than the output of the addressing message, for example, via a different data line or a different data bus.

[0027] According to advantageous embodiments of the method according to the invention, this further comprises storing the at least one frame byte from the HART data frame in a buffer memory and receiving a data retrieval request VEG745 8

[0028] from the processor, wherein the output of at least one frame byte from the HART data frame to the processor occurs in response to receiving the data retrieval request from the processor. Thus, the frame bytes are initially stored in the buffer memory and only output upon receipt of the data retrieval request. Consequently, the processor does not need to be ready to receive the frame bytes immediately after receiving the addressing notification. Rather, the output of the frame bytes only occurs in response to the processor's data retrieval request to the HART modem unit. The buffer memory is preferably an internal buffer of the HART modem unit. However, it is also possible for the buffer memory to be located outside the HART modem unit. The data retrieval request preferably occurs via the same mechanism or the same data line as the output of the addressing notification.However, it is also possible that the data retrieval request is made via a different communication channel, for example via a different data line or a different data bus.

[0029] The HART data frame is preferably a master frame, and the method preferably further comprises the following steps: receiving a send request from the processor, wherein the send request includes send data, and outputting the send data in a slave frame via the HART interface. The master frame is preferably a HART data frame originating from a master device. The slave frame is preferably a HART data frame originating from a slave device and generated in response to the master frame. The slave device is preferably a field device, of which the HART modem unit is a part. Preferably, the slave frame is addressed to the master device.

[0030] The send data is preferably data to be sent via the HART interface in a HART data frame. The send data preferably includes all data to be sent in the slave frame. It is therefore possible for the send data to completely specify the content of a HART data frame to be sent. However, it is also possible for the send data to contain only a portion of the data to be sent, for example, payload data for a data field in the slave frame, a HART command byte, and / or an address for an address field in the slave frame. Contents of other data fields, such as a preamble field or VEG745 9, are also possible.

[0031] The parity field of the slave frame is preferably generated by the HART modem unit. Thus, the HART modem unit advantageously performs protocol-level functions even when sending HART data frames. The output of the transmitted data preferably includes FSK modulation of the HART data frame onto a signal present at the HART interface.

[0032] According to a further aspect of the invention, a HART modem unit is proposed, comprising a HART interface, a communication interface for communicating with a processor, and a data processing unit. The HART modem unit is configured to perform the method described above. The HART interface can be a connector to which a two-wire line, preferably carrying a HART signal, can be connected. According to the invention, the data processing unit can be a microcontroller or a group of integrated circuits. The data processing unit preferably includes means that allow FSK demodulation of a HART signal. Furthermore, the data processing unit is preferably configured to extract a HART data frame from the digital data sequence.

[0033] The HART modem unit is preferably configured not only to receive and evaluate HART signals, but also to output HART signals via the HART interface. Thus, the HART modem unit preferably also includes means for performing FSK modulation of a HART data frame onto a signal present at the HART interface. The HART modem unit has a communication interface that allows it to be coupled with a processor. The communication interface can, for example, be configured to allow connection to a system bus or an on-chip bus, so that data and / or notifications can be output to and / or received from the processor. According to the invention, it is possible for the entire functionality of the HART modem unit to be implemented by an ASIC. Alternatively, the HART modem unit can also be implemented by several independent hardware modules.The HART modem unit can, for example, be embedded in its own housing or arranged on a printed circuit board. VEG745 10.

[0034] According to a further aspect of the invention, a computer program product for processing HART signals is proposed, comprising instructions that cause the HART modem unit to execute the method described above. The computer program product can thus be formed by a sequence of executable instructions and / or data. The executable instructions and / or data can, for example, be stored on a computer-readable medium and / or in non-volatile memory.

[0035] According to a further aspect of the invention, a method for processing and receiving HART signals by a HART modem unit and a processor is proposed. The method comprises at least the following steps: receiving an FSK-modulated signal by the HART modem unit via a HART interface of the HART modem unit, demodulating the FSK-modulated signal by the HART modem unit into a digital data sequence, extracting a HART data frame from the digital data sequence by the HART modem unit, and comparing a first address encoded in an address field of the HART data frame with a second address by the HART modem unit. If the first address matches the second address, the HART modem unit preferably outputs an addressing notification to the processor. Preferably, the processor subsequently receives the addressing notification.It is understood that these and subsequently described procedural steps can be combined in any way with the procedural steps described at the beginning, which are performed exclusively by the HART modem unit. Advantageously, the addressing notification is output by the HART modem unit as soon as a header of the HART data frame has been completely extracted and / or evaluated.

[0036] The processor can be, for example, a microcontroller or other computing unit of a field device. In particular, the processor can serve as a control unit of a field device. The addressing notification is preferably only output to the processor if the first address matches the second address. According to the invention, the addressing notification can be transmitted via a data bus or other data line that connects the processor to the HART modem unit. According to an advantageous embodiment of the invention, the VEG745 11

[0037] Address notification for an interrupt. According to advantageous embodiments of the method according to the invention, it is possible for the notification to be received by the processor via an interrupt line and / or to trigger an interrupt in the processor.

[0038] According to the invention, it is possible for the processor to switch from a sleep mode to an operating mode in response to receiving the addressing notification. In one advantageous embodiment of the invention, this can be triggered by the interrupt mentioned above. In other embodiments of the invention, the processor does not switch from a sleep mode, but from another mode to the operating mode, for example, from a power-saving mode or a wait mode. In the sleep mode, the processor consumes less energy than in the operating mode and / or computs more slowly than in the operating mode. In other embodiments of the invention, receiving the addressing notification merely causes the processor to execute a subroutine that prepares it to receive data from the HART modem unit and / or causes it to request data from the HART modem unit.

[0039] Preferably, the method further comprises the output of at least one frame byte from the HART data frame to the processor by the HART modem unit, wherein the HART data frame is a master frame, and the receipt of the at least one frame byte from the HART data frame by the processor. In response to the at least one frame byte, the processor preferably generates transmit data. The transmit data is preferably intended for transmission in a slave frame. Furthermore, the HART modem unit preferably issues a transmit request to the processor, wherein the transmit request contains the transmit data. Preferably, the HART modem unit receives the transmit request from the processor and outputs the transmit data via the HART interface in a slave frame.

[0040] According to the method variant described above, the HART modem unit transmits frame bytes from a master frame to the processor. According to the invention, the master frame can originate from a master device. The master frame can contain a master command, for example, a data request or a command to be executed by an actuator. In response to the at least one frame byte from the HART data frame, the processor can, according to VEG745 12

[0041] In advantageous embodiments of the invention, at least one action is performed. According to the invention, this at least one action can be reading measurement data from a sensor, for example, from a sensor, or issuing a command to an actuator.

[0042] In response to at least one frame byte, the processor can generate transmit data for the slave frame. This transmit data can advantageously include a measurement value and / or confirmation that an instruction has been executed by an actuator. However, the transmit data can also contain any other information. According to one variant of the procedure, the transmit data can contain only data for one data field of the slave frame according to the HART standard. According to other variants, the transmit data can contain content for additional fields or for all fields of the slave frame. To initiate the transmission of the slave frame to the master device, the processor issues the transmit request to the HART modem unit. This can be done, for example, via a system bus, an on-chip bus, or another data connection between the processor and the HART modem unit.

[0043] According to another embodiment of the method, error checking is performed during the demodulation of the FSK-modulated signal and / or during the extraction of the HART data frame by the HART modem unit. If an error is detected during error checking, the HART modem unit, according to this embodiment of the method, sends an error notification to the processor. The processor receives the error notification and, in response to the error notification, generates transmit data. According to the invention, the processor, according to this embodiment of the method, sends a transmit request to the HART modem unit, wherein the transmit request includes the transmit data. Furthermore, the HART modem unit receives the transmit request from the processor and outputs the transmit data via the HART interface. According to the invention, it is possible for the HART modem unit to generate a HART data frame based on the transmit data and to modulate the HART data frame onto a signal at the HART interface.

[0044] The procedure can be designed such that the HART modem unit does not send the addressing notification to the processor if it sends the error notification to the processor. However, it is also possible for the HART modem unit to send both the addressing notification and the VEG745 13

[0045] It sends an error notification to the processor. The addressing notification and the error notification can be transmitted either separately or in the same data packet.

[0046] Following an initial error handling approach, the processor executes an error handling routine in response to the error notification. According to the invention, the processor can handle the error based on the error notification. The processor can receive at least one frame byte from the HART modem unit, which may optionally contain errors. For error handling, the processor can, for example, correct erroneous data or skip this data during processing. If the error has been successfully handled, the processor can subsequently perform at least one action. According to the invention, this at least one action can be reading measurement data, for example from a sensor, or issuing a command to an actuator. The processor can also generate transmit data in this case, according to the invention.The transmitted data can advantageously include a measurement value and / or confirmation that a command has been executed by an actuator.

[0047] According to a second approach to error handling, the processor generates send data in response to the error notification, indicating the type of error. It is also possible to generate send data that simply indicates that an error has occurred. In an advantageous embodiment of the invention, the send data may contain content for only one data field of a HART data frame to be sent, but it may also contain content for other fields or all fields of the HART data frame to be sent. The processor preferably generates the send data such that the HART data frame to be sent addresses a device that transmitted the erroneous data.

[0048] According to another aspect of the invention, a field device is proposed comprising a HART modem unit and a processor, wherein the HART modem unit has a HART interface, a communication interface for communication with the processor, and a data processing unit, wherein the processor has a connection interface for communication with the HART modem unit, wherein the HART modem unit and the processor VEG745 14

[0049] The field device is communicatively coupled to each other, and is configured to process and receive HART signals for the execution of the steps according to the method described above. According to the invention, the field device can comprise at least one sensor and / or at least one actuator. For example, the field device can be used to acquire measurement data and / or to perform control functions. The processor can be, for example, a microcontroller, but it can also be any other computing unit.

[0050] The processor is preferably configured to perform control, regulation, and / or system functions of the field device. The processor is preferably coupled to the HART modem unit via a data connection. According to the invention, the data connection can comprise one or more data lines. The data connection preferably comprises an on-chip bus and / or a system bus. The HART modem unit of the field device preferably corresponds to the HART modem unit described above. The processor is preferably a separate component from the HART modem unit. Preferably, the processor and the HART modem unit are separate components. However, the processor and the HART modem unit can be located close to each other. Thus, according to the invention, it is possible for them to be arranged on the same circuit board.

[0051] The field device is preferably configured to perform the aforementioned process steps, with the processor and the HART modem unit advantageously being set up to execute these process steps. Preferably, a computer program is stored in the processor and / or the HART modem unit, which, when executed, causes the processor and / or the HART modem unit to perform the process steps.

[0052] Further features and advantages of the invention become apparent from the drawings, which are intended to clarify the invention for the person skilled in the art, enabling them to carry it out. The drawings do not, however, limit the invention. Nevertheless, the drawings depict advantageous aspects of the invention, the features of which—even individually, if necessary—can be used to specify the invention to be protected. (See VEG745 15.)

[0053] Fig. 1 shows a schematic representation of a field device according to the invention.

[0054] Fig. 2 shows a flowchart of a method according to the invention, which is executed by a HART modem unit and a processor of the field device,

[0055] Fig. 3 shows a sequence diagram of communication between the HART modem unit, the processor and a remote station and

[0056] Fig. 4 shows a schematic representation of a HART signal across different protocol levels.

[0057] Fig. 1 shows a schematic representation of a field device 1 according to the invention. The field device 1 comprises a HART modem unit 2 and a processor 3. The HART modem unit 2 has a HART interface 4. Furthermore, the HART modem unit 2 has a data processing unit 35 and a buffer memory 36. A two-wire line 5 is connected to the HART interface 4, connecting the field device 1 to a remotely located counterpart. The HART modem unit 2 is communicatively coupled to the processor 3 via a data line 37 of the field device 1. The field device 1 also has a distance sensor 6. The distance sensor 6 acquires measured values, which are read by the processor 3 and subsequently output by the HART modem unit 2 to the counterpart via the HART interface 4.

[0058] Fig. 2 shows a flowchart of a method according to the invention, which is executed by the HART modem unit 2 and the processor 3 of the field device 1. Initially, the HART modem unit 2 is in a HART modem unit initialization state 7, and the processor 3 is in a processor initialization state 8. The processor 3 initializes the HART modem unit 2 with an address at which the field device can be addressed via the HART protocol. This is symbolized by a first dashed arrow 9, which points from the processor initialization state 8 to the HART modem unit initialization state 7.

[0059] When a HART signal is transmitted over the two-wire line, the HART modem unit 2 performs a receive step 10. In receive step 10, the HART modem unit 2 demodulates the FSK-modulated HART signal into a digital data sequence and extracts a HART-VEG745 16

[0060] Data frame from the digital data sequence. If an error occurs, the HART modem unit 2, starting from a first branch 11, assumes a communication end state 12 and discards the received HART data frame. The transition to the communication end state 12 triggers an error message from the HART modem unit 2 to the processor 3 via the data line, which is represented by a second dashed arrow 13. Starting from the communication end state 12, the HART modem unit 2 can repeat the receive step 10 upon receiving another HART data frame via the HART interface.

[0061] If no error occurs, the HART modem unit 2 compares a first address, encoded in an address field of the HART data frame, with a second address, where the second address is the address mentioned earlier with which the HART modem unit 2 was initialized by the processor 3. If the first address does not match the second address, then the HART data frame is not addressed to the field device. In this case, the HART modem unit 2 proceeds from a second branch 14 to the communication end state 12 and discards the received HART data frame. If the first address matches the second address, then the HART data frame is addressed to the field device. In this case, the HART modem unit 2 issues an addressing notification to the processor 3 and sends frame bytes from the HART data frame to the processor 3, which is represented by a third dashed arrow 15.

[0062] Starting from the processor initialization state 8, processor 3 is in a sleep mode. In a trigger step 16, processor 3 receives the error notification and / or the address notification. This causes processor 3 to transition from sleep mode to an operating mode. After receiving the address notification, the HART modem unit 2 also transmits the frame bytes from the HART data frame to processor 3.

[0063] Depending on whether the HART modem unit 2 issued the addressing notification or the error notification, the processor 3, starting from a third branch 38, executes either an action step 17 or an error handling step 18. In action step 17, the processor 3 causes the field device to output a measurement value from the distance sensor VEG745 17.

[0064] The processor reads the measured value and creates a response message containing the measurement. In error handling step 18, processor 3 evaluates the error and creates a response message containing the error type. Both action step 17 and error handling step 18 are followed by a send request step 19, in which processor 3 requests HART modem unit 2 to output a HART data frame via the HART interface. This is symbolized by a fourth dashed arrow 20, pointing from send request step 19 to a receive step 21 of HART modem unit 2.

[0065] In receive step 21, HART modem unit 2 receives the response message and associated instructions. In a subsequent output step 22, HART modem unit 2 outputs the response message generated by processor 3 via its HART interface as a HART data frame addressed to the remote endpoint. After output step 22, HART modem unit 2 can repeat receive step 10 if it receives another HART data frame via the HART interface, provided another HART signal is received. In a completion state 23, which follows send request step 19, processor 3 enters idle mode. Upon receiving another addressing notification or another error notification, processor 3 executes trigger step 16 again.

[0066] Fig. 3 shows a sequence diagram of communication between the HART modem unit 2, the processor 3, and the remote device 24. First, the remote device 24 sends a master frame message 25 over the two-wire line to the HART modem unit 2, which contains a master frame. The remote device 24 is a master device. The master frame message 25 is transmitted as an FSK-modulated signal. After demodulating the FSK-modulated signal into a digital data sequence and extracting the master frame from the digital data sequence, the HART modem unit 2 compares a first address, encoded in an address field of the master frame, with the second address pre-stored in the HART modem unit 2, which can be used to address the field device 1.

[0067] The first address matches the second address. Therefore, HART modem unit 2 sends an addressing notification 26 to processor 3 via the data line between HART modem unit 2 and processor 3. VEG745 18

[0068] Furthermore, the HART modem unit 2 stores the master frame in its buffer. The processor 3 is switched from idle mode to operating mode by the addressing notification 26. The processor 3 then sends a data retrieval request 27 to the HART modem unit 2 via the data line. In response, the HART modem unit 2 sends a data message 28 containing several frame bytes from its buffer to the processor 3. The processor 3 evaluates the frame bytes and then reads measured values ​​from the distance sensor of the field device 1. The processor 3 transmits the measured values ​​as part of a send request 29 to the HART modem unit 2. In response to the send request 29, the HART modem unit 2 sends a slave frame message 30 to the remote device 24, transmitting the measured values ​​in a slave frame.

[0069] Fig. 4 shows a schematic representation of a HART signal across different protocol layers. The information shown at different protocol layers does not correspond directly to each other, but merely illustrates the principle of how the transmitted data is encoded. On a physical layer 31, logical values ​​are encoded using frequency-shift keying, where different frequencies are assigned to a logical one or a logical zero. A digital data sequence 32 is obtained from this by means of demodulation. Individual bytes in the digital data sequence 32 are encoded as UART frames 33. In the UART encoding format shown here, eight data bits D1 to D8 are enclosed by a start bit, a parity bit P, and a stop bit. Several bytes combined form a HART data frame 34.The HART data frame 34 shown here as an example has a preamble, a start byte (SD), an address (AD), a HART command byte (CD), a byte counter (BC), two status bytes (Status), data bytes (Data), and a parity byte (Parity). VEG745 19.

[0070] Reference symbol list

[0071] 1 field device

[0072] 2 HART modem units

[0073] 3 processors

[0074] 4 HART interface

[0075] 5 Two-wire line

[0076] 6 Distance sensor

[0077] 7 HART modem unit initial state 8 Processor initial state

[0078] 9 First dashed arrow

[0079] 10 Reception Step

[0080] 11 First branch

[0081] 12 Communication - Final state

[0082] 13 Second dashed arrow

[0083] 14 Second branch

[0084] 15 Third dashed arrow

[0085] 16 trigger step

[0086] 17 Action Step

[0087] 18 Error handling step

[0088] 19 Send request step

[0089] 20 Fourth dashed arrow

[0090] 21 Receipt step

[0091] 22 Output step

[0092] 23 Final state

[0093] 24 Counterpoint

[0094] 25 Master Frame Message

[0095] 26 Address notification 27 Data retrieval request

[0096] 28 Data message

[0097] 29 Send request

[0098] 30 Slave Frame Message

[0099] 31 Physical Layer

[0100] 32 Digital data sequence

[0101] 33 UART frames

[0102] 34 HART data frame VEG745 20

[0103] 35 Data processing unit 36 ​​Buffer storage

[0104] 37 Data line

[0105] 38 Third branch

Claims

VEG745 1 Patent claims 1. Method for processing HART signals by a HART modem unit (2), comprising: - Receipt of an FSK-modulated signal via a HART interface (4), - Demodulation of the FSK-modulated signal into a digital data sequence (32), - Extraction of a HART data frame (34) from the digital data sequence (32), - Comparison of a first address encoded in an address field of the HART data frame (34) with a second address, - if the first address matches the second address, output an addressing notification (26) to a processor (3).

2. Method according to claim 1, characterized by the fact that the addressing notification (26) is an interrupt.

3. Method according to any one of the preceding claims, characterized by the fact that The procedure further includes: - Error checking during demodulation of the FSK-modulated signal and / or during extraction of the HART data frame (34), - if an error is detected during error checking, an error notification is sent to the processor (3).

4. Method according to claim 3, characterized by the fact that the error is a parity error, a framing error or a gap error that is detected when extracting the HART data frame (34) from the digital data sequence (32).

5. Method according to one of claims 3 or 4, characterized by the fact that the output of the addressing notification (26) to the processor (3)VEG745 2 will not be performed if the error is detected and the HART data frame (34) does not require a response from the processor (3).

6. Method according to any one of the preceding claims, characterized by the fact that The procedure further includes: - Output of at least one frame byte from the HART data frame (34) to the processor (3).

7. Method according to claim 6, characterized by the fact that The procedure further includes: - Storing at least one frame byte from the HART data frame (34) in a buffer memory (36), - Receipt of a data retrieval request (27) from the processor (3), wherein the output of at least one frame byte from the HART data frame (34) to the processor (3) occurs in response to the receipt of the data retrieval request from the processor (3).

8. Method according to any one of the preceding claims, characterized by the fact that the HART data frame (34) is a master frame and the procedure further comprises: - Receipt of a send request (29) from the processor (3), wherein the send request (29) contains send data, - Output of the transmitted data in a slave frame via the HART interface (4).

9. HART modem unit (2) with a HART interface (4), with a communication interface for communication with a processor (3) and with a data processing unit (35), wherein the HART modem unit (2) is configured to execute the method according to any one of claims 1 to 8. VEG745 3 10. Computer program product for processing HART signals, comprising commands that cause the HART modem unit (2) according to claim 9 to execute the method according to any one of claims 1 to 8.

11. Method for processing and receiving HART signals by a HART modem unit (2) and a processor (3), comprising: - Receipt of an FSK-modulated signal by the HART modem unit (2) via a HART interface (4) of the HART modem unit (2), - Demodulation of the FSK-modulated signal by the HART modem unit (2) into a digital data sequence (32), - Extraction of a HART data frame (34) from the digital data sequence (32) by the HART modem unit (2), - Comparison of a first address encoded in an address field of the HART data frame (34) with a second address by the HART modem unit (2), - if the first address matches the second address, output of an addressing notification (26) to the processor (3) by the HART modem unit (2) and - Receipt of the addressing notification (26) by the processor (3).

12. Method according to claim 11, characterized by the fact that the processor (3) switches from a sleep mode to an operating mode in response to receiving the addressing notification (26).

13. Method according to one of claims 11 or 12, characterized by the fact that The procedure further includes: - Output of at least one frame byte from the HART data frame (34) to the processor (3) by the HART modem unit (2), where the HART data frame (34) is a master frame, - Receipt of the at least one frame byte from the HART data frame (34) by the processor (3), VEG745 4 - in response to at least one frame byte, generation of transmit data by the processor (3), - Output of a send request (29) to the HART modem unit (2) by the processor (3), wherein the send request (29) includes the send data, - Receipt of the transmit request (29) from the processor (3) by the HART modem unit (2), - Output of the transmitted data in a slave frame via the HART interface (4) by the HART modem unit (2).

14. Method according to any one of claims 11 to 13, characterized by the fact that The procedure further includes: - Error checking during the demodulation of the FSK-modulated signal and / or during the extraction of the HART data frame (34) by the HART modem unit (2), - if an error is detected during error checking, the HART modem unit (2) outputs an error notification to the processor (3), - Receipt of the error notification by the processor (3), - in response to the error notification, the processor generates transmit data (3), - Output of a send request (29) to the HART modem unit (2) by the processor (3), wherein the send request (29) includes the send data, - Receipt of the transmit request (29) from the processor (3) by the HART modem unit (2), - Output of the transmitted data via the HART interface (4) by the HART modem unit (2).

15. Field device (1) with a HART modem unit (2) and with a processor (3), wherein the HART modem unit (2) has a HART interface (4), a communication interface for communication with the processor (3) and a data processing unit (35), wherein the processor (3) has a connection interface for communication with the HART modem unit (2), wherein the HART modem unit (2)VEG745 5 and the processor (3) are communicatively coupled to each other, and wherein the field device (1) is configured to perform the steps according to one of claims 11 to 14.

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