JP4458279B2 - Programmable controller system communication method - Google Patents

Description

  The present invention relates to a communication method applied to a programmable controller (hereinafter referred to as PLC) system in which a communication master station and a communication slave station are connected by a field bus.

  Plural slaves that are masters that have communication functions and I / O terminals that have communication functions (input units, output units, input / output mixed units) are connected to the fieldbus, and output data is batched from master to slave. In the communication method of the PLC system in which the IN frame including the input data is sent back in a predetermined time zone, the technique for the master to know the status of the slave is already known. (For example, refer to Patent Document 1).

In a CSMA / CD bus (or network) represented by Ethernet (registered trademark), each node such as a master or a slave connected on the same bus (or network) is connected to the bus (or network). It is necessary to transmit data so as not to cause the above-mentioned data collision. A node that transmits data transmits data after first confirming the status of the bus (or network) in order to avoid collision of data on the bus (or network).
JP 2004-274396 A

  However, in the invention disclosed in Patent Document 1, the master only reads a specific status of the slave, and does not have means for actively reporting the status from the slave to the master. Also, in the CSMA / CD bus / network, each node can transfer data to each other, but the transfer efficiency decreases due to the occurrence of data collision.

  The present invention has been made paying attention to the above-mentioned problems, and the object of the invention is to transfer output data from the master to the slave in one OUT frame, and the slave is in a predetermined time zone. An object of the present invention is to provide a means for a slave to actively transmit data to a master in a communication method with high transfer efficiency in which an IN frame including input data is returned.

  Other objects and operational effects of the present invention will be easily understood by those skilled in the art by referring to the following description of the specification.

  In order to solve the above-described problems, the PLC system communication method of the present invention employs the following configuration.

  That is, according to the PLC system communication method of the present invention, a master that is a programmable controller having a communication function and a plurality of slaves that are I / O terminal devices having a communication function are connected to a fieldbus, and output data from the master to the slaves. In the PLC system communication method in which the master frame is transferred in one OUT frame and the slave returns the IN frame including the input data in a predetermined time zone, the master sends a message communication request in the OUT frame. One or a plurality of slaves whose presence / absence is to be confirmed are designated, and the slave designated by the OUT frame returns a response frame indicating the presence / absence of a message request.

  According to such a configuration, the output data is transferred from the master to the slave in a batch in one OUT frame, and the slave returns the IN frame including the input data in a predetermined time zone. While maintaining a good communication method, it is possible to provide means for the slave to actively transmit data to the master, and the responsiveness or functionality in this type of PLC system can be improved.

  In the communication method of the PLC system of the present invention, the slave specified by the OUT frame may return a response frame indicating the type of message in addition to a response frame indicating the presence or absence of a message request. According to such a configuration, the changed message type can be used as a determination element for the message acquisition necessity on the master side, and the degree of freedom of message acquisition on the master side can be improved.

  In the communication method of the PLC system of the present invention, the slave specified by the OUT frame may return a response frame indicating a message transmission request in addition to a response frame indicating the presence or absence of a message request. According to such a configuration, the slave is actually activated, and it is possible to transmit a message from the slave to the master.

  In the communication methods of the various PLC systems of the present invention described above, the master transmits a message transmission permission frame to the slave, passes the bus right to the slave, and the slave having the bus right sends a message to the master. You may make it transmit. According to such a configuration, it is possible to send a message including desired data to the master with the initiative of the slave while improving the flexibility of the slave by changing the initiative of the master / slave communication. It becomes.

  In a preferred embodiment of the communication method of the PLC system of the present invention, the content of the message transmitted from the slave can be the voltage of the power source supplied to the slave. According to such a configuration, the voltage of the power supplied to the slave can be confirmed on the master side as necessary.

  In a preferred embodiment of the communication method of the PLC system of the present invention, the content of the message transmitted from the slave can be an accumulated value of the number of communication errors detected by the slave. According to such a configuration, the cumulative value of the number of communication errors detected by the slave can be confirmed on the master side as necessary.

  According to the present invention, the output data is transferred from the master to the slave in one OUT frame, and the slave returns the IN frame including the input data in a predetermined time zone. While maintaining the method, it is possible to provide a means for the slave to actively transmit data to the master, and this can be used to improve the responsiveness or functionality in this type of PLC system. Can do.

  Hereinafter, a preferred embodiment of a communication method for a PLC system of the present invention will be described in detail with reference to the accompanying drawings.

  A block diagram of a PLC system including a master and a slave is shown in FIG. As shown in the figure, this PLC system includes a master (M) which is a PLC 1 having a communication function and one or more slaves (S) which are I / O terminals 2 having a communication function. (Bus type network) 6 is connected.

  Further, a repeater (R) that functions as the relay station 4 is interposed in one or more stages on the path connecting the master (M) and the predetermined slave (S) on the field bus 6. Has been. FIG. 7 shows the case where no repeater (R) exists in the path connecting the master station (M) and the slave station (S), and the case where one repeater (R) is interposed in the path. A network in a form in which two repeaters (R) are intervened in the route is shown. Note that 3 is a PC, and 5 is a termination device that reduces reflection at the termination of the fieldbus 6.

  The illustrated PLC 1 has a number of connectors arranged on a backplane (not shown) on which a parallel bus is laid, and a CPU unit, an I / O unit, various other special function units, etc. are arbitrarily connected to these connectors. A so-called building block type PLC that can be mounted is adopted.

  In particular, in this example, the “PLC having a communication function” 1 that functions as the communication master station (M) is configured by mounting the communication master unit 10 on one connector on the backplane. In the figure, among these units, only the CPU unit 20 and the communication master unit 10 are denoted by reference numerals.

  A hardware configuration diagram showing the internal configuration of the communication master unit 10 is shown in FIG. As shown in the figure, the communication master unit 10 includes a communication interface (communication I / F) 801 functioning as a communication physical layer, and a master ASIC 802 formed by implementing a circuit for realizing a desired communication function as an LSI. , A buffer area for transmission / reception data transferred to / from the CPU unit 20, a RAM 803 functioning as a calculation work area for the CPU 806, which will be described later, and a CPU 806 that is configured mainly by a microprocessor and controls the entire apparatus. A nonvolatile memory (EEPROM) 805 in which various setting data are stored, an LED display unit 807 for performing various operation displays, and a setting switch (setting SW) 808 used for various setting operations. And functioning as an interface to the internal bus leading to the CPU unit 20 Bus interface and an (internal bus I / F) 804.

  As is well known to those skilled in the art, in this type of PLC system, the CPU unit (see FIG. 7) 20 repeatedly performs common processing, I / O refresh processing, user program execution processing, peripheral service processing, and the like. When the I / O refresh process is executed, the RAM 803 in the communication master unit 10 is not limited to the local I / O unit (not shown) mounted on the backplane. I / O refresh processing is also executed between the I / O shared area.

  Specifically, the OUT data in the I / O memory (not shown) of the CPU unit 20 is transferred to the OUT area in the RAM 803 of the communication master unit 10, and the IN data in the IN area of the RAM 803 is transferred to the I / O memory of the CPU unit 20. / O Transferred to the IN area in the memory. These operations are executed by the MPU in the CPU unit 20.

  On the other hand, as will be described in detail later, communication between the communication master unit 10 and each I / O terminal device (slave S) 2 via the field bus 6 is asynchronous with the I / O refresh operation of the CPU unit 20. As a result, a kind of I / O refresh processing is also executed between each I / O terminal device 2 and the RAM 103 in the communication master unit 10. These operations are executed by the MPU in the communication master unit 10.

  Specifically, the IN data received from the I / O terminal device 2 that is the slave (S) is written in the IN area of the RAM 803 in the communication master unit 10, and the OUT data in the OUT area of the RAM 803 corresponds to the corresponding data. To the I / O terminal device 2 to be transmitted.

  In this way, the I / O refresh process is executed between the I / O memory in the CPU unit 20 and each I / O terminal device 2, 2,... As described above, the CPU unit 20 can handle I / O devices connected to the remotely installed I / O terminal devices 2, 2,.

  Next, FIG. 9 shows a hardware configuration diagram inside the I / O terminal which is the slave (S). As shown in the figure, the I / O terminal device 2 is for a slave that is an LSI having a communication interface (communication I / F) 901 functioning as a communication physical layer and a circuit for realizing a desired communication function. An ASIC 902, a CPU 903 mainly composed of a microprocessor for controlling the entire apparatus, a non-volatile memory (EEPROM) 908 for storing various setting data, and an LED display for displaying various operations Unit 907, a setting switch (setting SW) 906 used for various setting operations, an external interface unit (I / F) unit 903 for exchanging data with the I / O device, and the entire apparatus And a DC power supply unit 904 having a transformer function for supplying a stabilized DC power supply.

  Between the PLC 1 and each I / O terminal 2, one-to-N or one-to-one master-slave communication with the PLC 1 as a communication master (M) and each I / O terminal 2 as a communication slave station (S). Through this, I / O data and various message data are exchanged.

  Speaking of I / O data, specifically, OUT data received from the PLC 1 is sent to the I / O device via the I / F unit 207 of the I / O terminal device 2, and the I / O device. The IN data taken into the I / O terminal device 2 via the I / F unit 903 is transmitted to the PLC device 1. The exchange of these input / output data will be described in more detail later.

  Next, a communication protocol employed by the communication method of the PLC system according to the present invention will be described with reference to FIG.

  The master manages the start timing of this protocol. As shown in FIG. 1, the communication cycle includes an OUT frame (100) transmitted from the master, CN frames (110) to (11n) transmitted from the slave specified by the OUT frame to the master, and an IN slave. This is followed by IN frames (120) to (12m) to be transmitted.

  The start timing of the communication cycle between the master unit (M) and each slave (S) is timed when normal reception of the OUT frame (100) is completed. Since the CN frames (110) to (11n), the IN frames (120) to (12m), and the number of frames to be transmitted are fixed, the transmission timing of each frame is the OUT frame (100). The normal transmission completion can be performed by monitoring the time determined as the start timing.

  An example of the structure of the OUT frame is shown in FIG. The OUT frame (100) includes a “start” 201 indicating the start of a frame, a “command” 202 indicating an OUT frame, a “CN_frame transmission request address” 203 indicating a slave requesting CN frame transmission, and a data length of OUT data. "Length" 204, "OUT data" 205 storing output data to the OUT slave and the MIX slave, and "CRC" 206 for detecting a frame abnormality.

  The master (M) manages where in the OUT frame the output data addressed to each OUT slave (output dedicated unit) or MIX slave (input / output mixed unit) is assigned, and each OUT slave Before the communication cycle starts, the master notifies the output data received by the station where the output data is assigned in the OUT frame.

  An example of the structure of the IN frame is shown in FIG. The IN frame includes a “start” 301 indicating the start of the frame, a “command” 302 indicating the IN frame type, an “address” 303 indicating the slave that transmitted the IN frame, and a “length” indicating the data length of the IN data. ”304,“ IN data ”305 storing input data from the IN slave and the MIX slave, and“ CRC ”306 for detecting a frame abnormality.

  The master (M) manages the time at which each IN slave or MIX slave transmits after receiving the OUT frame normally. Before the communication cycle starts, the master (M) sends each IN slave or MIX slave to each IN slave or MIX slave. The timing for transmitting the IN frame is notified. Each IN slave or MIX slave holds a value of the timing to transmit the IN frame notified from the master, and each IN slave or MIX slave transmits an IN frame according to the value.

  The IN frame or the MIX slave can transmit the IN frame to the master. However, since the OUT slave cannot issue the IN frame, the IN frame cannot have a means for making a message communication request. For this reason, the CN frame that can be issued by all types of slaves is provided with means for making a message communication request.

An example of the structure of the CN frame is shown in FIG. CN frame shows the "start" 401 indicating the start of a frame, and shows the CN frame "command" 402, and the CN frame indicating the transmission slave "Address" 403, the message type or a message transmission request An “alarm” 404 and a “CRC” 405 for detecting a frame abnormality are included.

  An example of correspondence between alarm bits and message types is shown in FIG. The “alarm” 404 includes a single bit or a plurality of bits, and the correspondence between the alarm bit and the message type is established in advance between the master and each slave.

  An example of the “command” field of the CN frame is shown in FIG. The “command” field has a bit indicating whether or not there is a message transmission request of the slave that transmitted the CN frame.

  Next, the outline of the master and slave operations executed in connection with the present invention will be described with reference to the flowcharts of FIGS.

  FIG. 15 is a flowchart showing master processing (firmware operation) in the I / O communication cycle, and FIG. 16 is a flowchart showing master processing (OUT frame transmission operation by the ASIC) in the I / O communication cycle. It is shown.

  The processing shown in FIG. 15 is periodically executed by timer interruption by the I / O communication cycle timer. When the process is started, first, the presence or absence of an alarm bit is determined in the CN frame (step 1501). Only when there is an alarm bit (YES in step 1501), the content of the alarm bit is notified to the PLC (step 1502). ).

  Subsequently, the presence or absence of a CN frame message request is determined (step 1503), and only when there is a message request (step 1503 YES), that fact is registered in the message queue (step 1504).

  Subsequently, it is determined whether or not there is a transmission request in the message queue (step 1505), and only when there is a transmission request (step 1505 YES), message transmission processing is executed (step 1506).

  After that, after executing OUT frame creation processing (step 1507), CN frame transmission request address creation processing (step 1508) used in the next processing, and I / O communication cycle timer activation processing (step 1509). OUT frame transmission activation processing (step 1510) is executed.

  Referring to FIG. 16, on the ASIC 802 side, when the OUT frame transmission process starts, the start code transmission process (step 1601), the command set in the firmware, the CN frame transmission, the request address, OUT After data transmission (step 1602), CRC transmission processing (step 1603) is performed, and the transmission processing ends.

FIG. 18 is a flowchart showing slave processing (I / O cycle processing by ASIC) in the I / O communication cycle. FIG. 18 is a flowchart showing slave processing (I / O cycle processing by firmware) in the I / O communication cycle. Are shown in FIG.

  In FIG. 18, when I / O communication cycle processing is started, normal reception of an OUT frame is determined (step 1801), and when abnormal reception is determined (NO in step 1801), communication error count addition processing is executed. (Step 1802). On the other hand, if the OUT frame is normally received (step 1801 YES), it is determined whether the own apparatus is an OUT slave or a MIX slave (step 1803).

  Here, when the determination is affirmative (step 1803 YES), the OUT reception interrupt generation process (step 1804) is executed, whereas when the determination is negative (step 1803 NO), CN frame transmission is performed. Timer activation processing is executed (step 1805). Subsequently, it is determined whether the own device is addressed to the IN slave or the MIX slave (step 1803).

  Here, if the determination is affirmative (YES at step 1806), the IN frame transmission timer activation process (step 1807) is executed, whereas if the determination is negative (NO at step 1806), the local station determines that the CN is CN. A determination is made as to whether it is a frame request address (step 1808).

  Here, in the case of an affirmative determination (YES in step 1808), the CN frame transmission timer is timed up (YES in step 1809), and the CN frame transmission process (step 1810) is executed, whereas in the case of a negative determination (Step 1808 NO), it is determined whether the own device is an IN slave or a MIX slave (step 1811).

  If the determination is affirmative (YES in step 1811), the IN frame transmission timer is awaited (YES in step 1812), and after the IN frame transmission process (step 1803) is executed, the I / O communication cycle process is performed. In contrast, if the determination is negative (NO in step 1811), the I / O communication cycle process is immediately terminated.

  As shown in FIG. 19, in the OUT frame reception interrupt, data corresponding to the slave is read (step 1901) and written to the ASIC I / O output register (step 1902). In addition, in the IN refresh process, an ASIC I / O input register read process (step 1911), an IN frame creation process (step 1912), and an IN refresh timer start process (step 1903) are executed.

  Next, data transfer in the I / O communication cycle between the master and each slave performed using the above-described frame and master / slave functions will be described in time series.

  [1] First, the master unit generates and transmits an OUT frame. At this time, a slave requesting transmission of a CN frame is designated in “CN_frame transmission request address”. Regarding the method of specifying the slave, whether the CN frame is transmitted only to the slave having the address written in this field, or whether a plurality of slaves having a range of addresses from the address written in this field transmit the CN frame, Either one is acceptable if it is determined in advance.

  [2] The OUT slave and the MIX slave that have normally received the OUT frame take in the data corresponding to their own station in the “OUT data”.

[3] "CN_frame transmission request address" slave instructed a transmission request for the CN frame in returns the CN frame regardless of the message transmission request. The master can confirm that the slave of the address is connected by returning the CN frame regardless of the presence or absence of the message. When a plurality of slaves return CN frames, it is necessary to shift the timing at which each slave transmits a CN frame in the same manner as the IN frame so that the CN frames do not collide.

  [4] The IN slave and the MIX slave that have normally received the OUT frame transmit the IN frame to the master in accordance with a predetermined IN frame transmission timing.

  Note that the master can confirm the presence / absence of message transmission requests of all slaves by sequentially changing the CN transmission request address and transmitting the OUT frame.

  15 to 17 show the processing flow of the master during the I / O communication cycle described above, FIGS. 18 and 19 show the processing flow of the slave, and FIG. 20 shows the structure of the message queue shown in FIGS. ing. The message queue is accessible from the master and the PLC.

  Next, message communication will be described. The structure of the frame used for message communication is shown in FIG. The message frame includes a “start” 1001 indicating the start of the frame, a “command” 1002 indicating the message frame, a “destination address” 1003 indicating the destination node of the message frame, and a node indicating the node that transmitted the message frame “ “Source address” 1004, “Length” 1005 indicating the data length of the message data, “Message data” 1006 corresponding to the message type, and “CRC” 1007 for detecting a frame abnormality.

  There are several uses for message frames: frames that allow message frames to be transmitted, event frames for transferring data, ACK frames that indicate that message data has been received normally, and BUSY frames that indicate that message data cannot be received These are distinguished by using the “command” field described above. The “message data” is not always present.

  The “command” field of the message frame is shown in FIG. Unlike the I / O communication cycle shown in FIG. 1, the message frame is transmitted and received in a communication cycle called a message communication cycle. The relationship between the communication cycle and the message cycle is shown in FIG. The message communication cycle is inserted only when the master sends a message or when the slave requests message communication from the master and the master permits it.

  First, a case where a message is first transmitted from the master to the slave will be described. When a message type for requesting message communication from the master to the slave is specified in the previous CN frame, the master transmits a message to the slave according to its importance. The flow of message communication in this case is shown below.

  [1] The master transmits “start” 1001, “command” 1002 indicating an event frame, “destination address” 1003 as the address of the slave that requested message transmission, and “source address” 1004 as the address of the local station. The data length corresponding to the message data amount is “length” 1005, the message content is “message data” 1006 and “CRC” 1007, and the message frame is transmitted.

  [2] The slave determines whether it is addressed to its own station based on “destination address” 1003. If it is not addressed to the local station, the frame is discarded.

  [3] A slave that is determined to be addressed to itself by “destination address” 1003 “start” 1001, “command” 1002 indicating an ACK frame, and “master address” “destination address” 1003 when the frame is normally received. The address of the own station is set to “source address” 1004 and “CRC” 1007, and the message is transmitted. If the frame cannot be normally received, “start” 1001, “command” 1002 indicating a BUSY frame, master address “destination address” 1003, own station address “source address” 1004, and data length “0” are set. Set "Length" 1005, appropriate value to "CRC" 1007, and send the message.

  FIG. 12 shows a message cycle when a message is transmitted from the master to the slave. As shown in FIG. 12, a plurality of event frames may be transmitted and received within one message communication cycle.

  Next, a case where a message is transmitted from the slave to the master will be described. The flow of message communication in this case is shown below.

  [1] The master has a “start” 1001, a “command” 1002 indicating a message transmission permission frame, a “destination address” 1003 as the address of the slave that has requested the message transmission permission, and a “source address” 1004 as the address of the local station. The data length “0” is set to “length” 1005, the appropriate value is set to “CRC” 1007, and the message frame is transmitted.

  [2] The slave determines whether it is addressed to its own station based on “destination address” 1003. If it is not addressed to the local station, the frame is discarded.

  [3] The slave determined to be addressed to the own station by “destination address” 1003 is “start” 1001, “command” 1002 indicating an event frame, master address is “destination address” 1003, and transmission source master address is “ “Source address” 1004, data length corresponding to the amount of message data to be transmitted “length” 1005, message contents “message data” 1006, “CRC” 1007 are set, and the message is transmitted.

  [4] The master and the slave determine whether or not they are addressed to their own stations based on the “destination address” 1003. If it is not addressed to the local station, the frame is discarded.

  [5] A master that has been determined to be addressed to itself by “destination address” 1003 “start” 1001, “command” 1002 indicating an ACK frame, and “source address” as the message source address when the frame is normally received 1003, “Origin address” 1004 and “CRC” 1007 are set as the address of the own station, and the message is transmitted. If the frame cannot be received normally, “Start” 1001, “Command” 1002 indicating a BUSY frame, “Destination address” 1003 as the source address of the message, “Source address” 1004 as the address of the own station, and “CRC” 1007 Set and send a message.

  FIG. 13 shows a message cycle when a message is transmitted from the slave to the master. As shown in FIG. 13, within one message communication cycle, the master may transmit a plurality of message transmission permission frames and allow the slave to transmit a plurality of event frames.

  In the present invention, specific examples in which message communication is performed between a slave and a master include the following.

  [1] The slave monitors the power supply voltage supplied to the slave, and when the monitor value exceeds a certain threshold, the slave uses the CN frame to notify the master of an abnormal power supply voltage value. Notice. A system that judges power failure only by this notification, and further, the master sends a message communication permission frame to the slave, and the slave that is allowed to send a message uses the message frame to specify a specific power supply voltage value, A system that notifies the master can be considered.

  [2] The slave monitors the number of communication errors, and when the monitored value exceeds a certain threshold, the slave notifies the master of an alarm with frequent communication abnormalities using the CN frame. A system that determines a communication error based only on this notification, and the master sends a message communication permission frame to the slave, and the slave that is permitted to send a message uses the message frame to indicate the specific number of occurrences to the master. A system for notification may be considered.

  As a specific example, an example in which the number of communication errors is detected and the number of errors is reported will be described.

  [1] The slave firmware periodically monitors the “communication error count” shown in FIG. 18 to see if the threshold is exceeded. If the threshold is exceeded, the alarm bit of the CN frame is set.

  [2] As shown in FIG. 15, the master firmware sequentially updates the CN frame transmission request address and transmits the OUT frame, so that the OUT containing the slave address in the CN frame transmission request address field will be included. A frame is transmitted.

  [3] As shown in FIGS. 18 and 19, the slave transmits the CN frame including the alarm bit set in [1] because the address of the local station is included in the CN frame transmission request address field.

  [4] As shown in FIGS. 15 to 17, the master ASIC stores the contents of the alarm of the received CN frame and the presence / absence of a message transmission request in a memory area in the ASIC.

  [5] As shown in FIGS. 15 to 17, in the next I / O communication cycle, the master firmware confirms the content of the alarm message and reports to the PLC that the number of communication errors exceeds the threshold.

  [6] Although it depends on the application of the PLC, here, a case where the number of communication errors is read will be described. In this case, the PLC instructs the master to read the number of communication errors.

  [7] The master that is instructed to read the communication error count registers a message transmission request in the message queue, which means a communication error count read request. Since the message queue is executed every I / O communication cycle, the message request is eventually read out.

  [8] As shown in FIGS. 15 to 17, when the message request registered in [7] is read, the master firmware sends an event frame indicating the slave as a destination and the message as message data. Create and send a message. After the time required for the message communication cycle as shown in FIG. 12 elapses, the master firmware shifts to “OUT frame generation” processing.

  [9] The slave ASIC that has received the request to read the number of communication errors returns an ACK frame or a BUSY frame and notifies the firmware of an event frame reception interrupt.

  [10] The firmware of the slave that has received the interrupt reads the data from the register storing the number of communication errors in the ASIC, and creates an event frame including the value. When the creation of the event frame is completed, a CN frame with a message transmission request is set.

  [11] Similar to [2], [3], and [4], the CN frame set in [10] will eventually be stored in the ASIC of the master.

  [12] As shown in FIGS. 15 to 17, in the next I / O communication cycle, the master firmware recognizes that there is a message transmission request from the slave and sends a message transmission permission frame to the message queue. Register with. Similar to [7], since the message queue is executed for each I / O communication cycle, the message request is eventually read out.

  [13] As shown in FIGS. 15 to 17, when the message request registered in [12] is read, the master firmware creates a message transmission permission frame indicating the slave at the destination, Send. After the time required for the message communication cycle as shown in FIG. 13 has elapsed, the master firm proceeds to the “out frame generation” process.

  [14] The slave ASIC that has received the message transmission permission frame transmits the event frame created in the item 10.

  [15] The master ASIC that has received the event frame returns an ACK frame or a BUSY frame, and notifies the firmware of an event frame reception interrupt.

  [16] The master firmware that has received the interrupt notifies the PLC of the number of communication errors included in the event frame.

  According to the present invention, the output data is transferred from the master to the slave in one OUT frame, and the slave returns the IN frame including the input data in a predetermined time zone. While maintaining the method, it is possible to provide a means for the slave to actively transmit data to the master, and this can be used to improve the responsiveness or functionality in this type of PLC system. Can do.

It is a figure showing the flame | frame transmitted / received in a communication cycle. It is a figure which shows the structure of OUT frame. It is a figure which shows the structure of IN frame. It is a figure which shows the structure of CN frame. It is the figure which showed the response | compatibility of an alarm bit and a message. It is the figure which showed the meaning of the command field of CN frame. It is a block diagram of a PLC system. It is a block diagram of a master unit. It is a block diagram of a slave unit. It is a figure which shows the structure of a message frame. It is a figure which shows the relationship between an I / O communication cycle and a message communication cycle. It is a figure showing the message cycle in the case of transmitting a message from a master to a slave. It is a figure showing the message cycle in the case of transmitting a message from a slave to a master. It is the figure which showed the meaning of the command field of a message frame. It is a flowchart which shows the process (firmware operation | movement) of the master of an I / O communication cycle. It is a flowchart which shows the process (OUT frame transmission operation by ASIC) of the master at the time of an I / O communication cycle. It is a flowchart which shows the process (frame reception operation | movement by ASIC) of the master at the time of an I / O communication cycle. It is a flowchart which shows the process (I / O cycle process by ASIC) of the slave at the time of an I / O communication cycle. It is a flowchart which shows the process (process of the I / O cycle by firmware) of the slave at the time of an I / O communication cycle. It is a figure which shows an example of the structure of a message queue.

Explanation of symbols

1 PLC
2 I / O terminal 3 PC
4 Relay station 5 Termination device 6 Bus network 10 Communication master unit 20 CPU unit 801 Communication I / F
802 ASIC for master
803 RAM
804 Internal bus I / F
805 EEPROM
806 CPU
807 LED display 808 Setting SW
901 Communication I / F
902 Slave ASIC
903 I / O unit 904 Power supply 905 MPU
906 Setting SW
907 LED display 908 EEPROM

Claims (3)

A plurality of slaves are I / O terminals with a master communication function is a programmable controller having a communication function is connected to the field bus, to collectively output data from the master to the slave transferred by one OUT frames, wherein The slave is a communication method of the PLC system in which each IN frame including input data is returned at a predetermined time zone.
The master designates one or more slaves whose operation status is to be confirmed in the OUT frame and transmits them together with the output data, and the slave designated in the OUT frame defines a response frame as the predetermined time zone. Return them at different times ,
The response frame includes information indicating the presence / absence of a message communication request from the slave, and information indicating the message content,
The message content is information on whether or not an abnormality is detected in the voltage of the power supply supplied to the slave, and / or information on whether or not the cumulative value of the number of communication errors detected by the slave exceeds a predetermined threshold, communication method PLC system characterized in that it. The slave transmits a response frame regardless of the presence / absence of a message communication request from the slave and the message content, and when the master receives the response frame, the slave communicates with the slave joining the network. The PLC system communication method according to claim 1, wherein it is determined that the communication is normally performed . Slave the master when receiving the response frame indicating that there is a transmission request from the slave, which sends a message transmission permission frame to the slave, the bus passes to the slave, with the bus communication method PLC system according to claim 1 or 2 but wherein, characterized in that, sending a message to the master.

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