JP2009055230A - Serial communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain saving of wiring without generating delay in a synchronous communication packet for which real time communication is required. <P>SOLUTION: This serial communication device is provided with: means (422, 442) for detecting possibility of collision among a communication packet including header information capable of identifying synchronous communication and asynchronous communication, the synchronous communication packet transmitted from a self-station, and an asynchronous communication packet input from other peripheral equipment; buffers (424, 444) for queuing communication packets provided to an input port; a means for outputting the synchronous communication packet as it is when the synchronous communication packet is received, performing buffering of the asynchronous communication packet to preferentially transmit the synchronous communication packet when generation of the collision with the synchronous communication packet transmitted from the self-station is predicted when the asynchronous communication packet is received; and a means for outputting the asynchronous communication packet as it is when it is judged that there is no generation of the collision. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a serial communication device, and in particular, it is possible to reduce the wiring between various devices connected by serial communication. The present invention relates to a serial communication device for performing synchronous communication and asynchronous communication via a serial communication path.

  In recent years, FA (factory automation) network systems have been designed to connect the host controller and multiple motor drive units via a serial communication path for the purpose of reducing wiring and increasing functionality, and to operate commands to motors via serial communication. Is becoming widely practiced. As an example of this, there is one in which Ethernet (registered trademark) or the like is applied to the physical layer of serial communication.

  An example of the configuration of a conventional FA network system is shown in FIG. In this FA network system, for example, a host controller 100 serving as a master device is connected to peripheral devices via a plurality of communication lines (servo control communication cable 300, I / O communication cable 310, camera communication cable 320 in the figure). (In the figure, it is connected to a motor driving device 210, a sensor 220, and a camera 230 for driving the servo motor 200), and transmits and receives data using serial communication or the like. Among them, the master communication controller 110 provided in the host control device 100 is the main communication performed in the FA network system, and is driven by a motor in response to a command transmission synchronized with the reference signal from the host control device 100. In general, master-slave communication in which the device 210 returns a response is performed. In FIG. 1, the host control device 100 corresponds to a master device, and the motor drive device 210 corresponds to a slave device.

  The host controller 100 includes an I / O interface 120 for communicating with the sensor 220 via the I / O communication cable 310 and a camera for communicating with the camera 230 via the camera communication cable 320. An interface 130 and a CPU 140 are included.

  The motor driving device 210 includes a servo controller 220 and a slave communication controller 230, and adjacent motor driving devices 210 are connected by a servo control communication cable 300.

  As illustrated in FIG. 2, the master communication controller 110 is connected to a communication I / F unit 112 connected to the servo control communication cable 300, a reference signal generation unit 114, an access control unit 116, and a CPU 140. The memory unit 118 is included.

  As illustrated in FIG. 3, the slave communication controller 230 converts the serial signal input from the lower side into a parallel signal and outputs the parallel signal to the line setting unit 236 or the parallel signal selected by the line setting unit 236 as a serial signal. From the lower-level communication I / F unit 232 that converts to the lower-level side and outputs to the lower side, the access control unit 234 connected to the servo controller 220 in the own station, and the lower-level communication I / F unit 232 or the access control unit 234 A line setting unit 236 for selecting a signal, and a parallel signal selected by the line setting unit 236 is converted into a serial signal and output to the upper side, or a serial signal input from the upper side is converted into a parallel signal. And a higher-level communication I / F unit 238 that outputs to the line setting unit 236.

  The command data transmitted from the host control device 100 is transmitted to the motor drive device 210, and the response data from the motor drive device 210 is transmitted to the host control device 100. The host controller 100 sequentially executes transmission / reception with the next motor driving device 210 when transmission / reception with one motor driving device 210 is completed, and transmission / reception with all motor driving devices 210 is completed. At that point, one communication cycle is complete. By repeating this communication cycle, real-time communication is performed. In addition to the motor driving device 210, devices such as the sensor 220 and the camera 230 are connected as peripheral devices.

  Another example of the FA network system is described in Patent Document 1, for example. In this technology, a host system, a motor drive device, and a serial encoder are connected to the same communication path and operated synchronously to realize sharing of various types of information, and to reduce wiring of the FA network system.

  In addition, the technology described in Patent Document 2 gives priority to communication packets, and retransmits communication packets with a low priority for communication nodes with a low priority for communication packets with a high priority. By overtaking, real-time communication is controlled and communication efficiency is improved.

JP 2006-50774 A Japanese Patent No. 3460080

  However, in the conventional configuration shown in FIG. 1, the master control device 100 serving as a master is connected to the peripheral devices 200, 220, and 230 via a plurality of serial communication paths 300, 310, and 320. There is a problem that the advantage of the reduced wiring, which is a large purpose of connection by serial communication, cannot be obtained sufficiently.

  Therefore, it is conceivable to connect all peripheral devices to the host controller 100 via the same serial communication path. However, communication means that requires high-precision synchronization means such as servo motor control performed by the master communication controller 110 and the I / O interface 120, camera interface 130, etc., which are sufficient with relatively low-precision control, are connected to the same communication path. In the case of connection via a high-precision synchronization means must be provided for all interfaces. Therefore, there is a problem that even if the interface is sufficient with relatively low accuracy control, the circuit scale increases and the cost becomes high.

  On the other hand, an interface sufficient for relatively low-accuracy control remains a communication unit (asynchronous communication) that does not require a high-accuracy synchronization unit, and all the peripheral devices are connected to the host controller 100 via the same serial communication path. It is also conceivable to connect to. However, simply mixing non-synchronized communication means (asynchronous communication) with communication means (synchronous communication) using high-precision synchronization such as servo motor control performed by the master communication controller 110 There is a problem in that a collision occurs between packets and a delay occurs in a communication packet provided with high-precision synchronization means.

  On the other hand, the technique described in Patent Document 2 solves the problem that the wiring saving is insufficient. However, the serial communication units of the host system, the motor drive device, and the serial encoder are connected to the same communication path. In order for the motor drive device and the serial encoder to perform processing in synchronization with the command information transmitted from the host system, a synchronization means for synchronizing the connected devices is required, which increases the circuit scale. There was a problem.

  In addition, the technique described in Patent Document 2 gives priority to communication packets in order to solve the problem of collision between communication packets, and when a communication packet collision occurs, high priority is given. The communication packet of the low priority communication packet is controlled to be overtaken without retransmitting the communication packet with a short delay time for each communication node, but the ESD (End) of the low priority communication packet (asynchronous communication) is controlled. of STREAM DELIMITER enters the high-priority communication packet (synchronous communication) area, the synchronous communication packet cannot be sent until the end of the asynchronous communication packet, and the high-priority communication packet that requires real-time communication (synchronous communication) Communication) has a problem of delay.

  The present invention has been made to solve the above-described conventional problems, and it is an object of the present invention to realize wiring saving without causing a delay in a synchronous communication packet that requires real-time communication.

  The present invention can identify synchronous communication and asynchronous communication in a serial communication device for performing synchronous communication and asynchronous communication between a plurality of peripheral devices and a control device via the same serial communication path using a communication packet. Means for detecting the possibility of collision between a communication packet including correct header information, a synchronous communication packet transmitted from the own station, and an asynchronous communication packet input from another peripheral device, and a communication packet standby provided at the input port When a synchronous communication packet is received, the synchronous communication packet is output as it is. When an asynchronous communication packet is received, if the occurrence of a collision with the synchronous communication packet transmitted from the local station is expected, it is asynchronous. A means for preferentially transmitting synchronous communication packets by buffering communication packets and asynchronous communication when it is determined that no collision has occurred. And means for outputting a packet as it is, by providing, is obtained by solving the above problems.

  Here, by identifying the upper layer protocol ID stored in the frame format of the communication packet, it is possible to identify whether it is a synchronous communication packet or an asynchronous communication packet.

  Further, the possibility of collision between the synchronous communication packet and the asynchronous communication packet can be determined from the timing information in the apparatus and the total length information stored in the frame format of the asynchronous communication packet.

  According to the present invention, in the FA network system, the synchronous communication packet synchronized with the reference signal of the host controller and the asynchronous communication packet from the general-purpose interface can be integrally transmitted to the same serial communication path. It is possible to reduce the wiring of the FA network system.

  Also, the same serial communication path as the communication means that requires high-precision synchronization means such as servo motor control while maintaining a general-purpose interface sufficient for relatively low-accuracy control without being provided with high-precision synchronization means Therefore, there is no increase in circuit and cost of peripheral devices with a general-purpose interface.

  Furthermore, when the input asynchronous communication packet collides with or may collide with the synchronous communication packet, the asynchronous communication packet is once stored in the buffer, and after the synchronous communication packet is output, it is output from the buffer. As a result, the asynchronous communication packet can be transmitted in a short time without being retransmitted.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The embodiment of the FA network system according to the present invention includes a master communication controller 410 and a slave communication controller 430 shown in FIGS. 5 and 6, respectively, as shown in FIG. In addition to the above configuration, the host controller 100, the motor drive device 210, the sensor 220 and the camera 230 connected to the hub 240 are connected by a single communication cable 330.

  As shown in detail in FIG. 5, the master communication controller 410 includes a communication I / F unit 412 connected to the communication cable 330, a reference signal generation unit 414, an access control unit 416, and a memory unit connected to the CPU 140. 418, a communication I / F unit 420 connected to the I / O interface 120 and the camera interface 130, a packet arbitration unit 422, and a buffer unit 424.

  As shown in detail in FIG. 6, the slave communication controller 430 converts the serial signal input from the lower side into a parallel signal and outputs it to the synchronous / asynchronous identifying unit 440 or the parallel signal selected by the line setting unit 436. Is converted into a serial signal and output to the lower side, the lower side communication I / F unit 432, the access control unit 434 connected to the servo controller 220 in the own station, and the lower side communication I / F unit 432 or the access control unit A line setting unit 436 for selecting a signal from 434, and a parallel signal selected by the line setting unit 436 is converted into a serial signal and output to the upper side, or a serial signal input from the upper side is converted into a parallel signal. The upper communication I / F unit 438 that converts and outputs the line setting unit 436 and the type of communication packet input to the input port are identified. A synchronous / asynchronous identification unit 440, a packet arbitration unit 442 is configured to include a buffer unit 444.

  An example of the serial communication system frame format used in this embodiment is shown in FIG. In the header portion of this communication packet, in addition to the network address (source address, destination address, etc.), an ID indicating a higher layer protocol stored in a data field that is next to be called a type field for multiplexing / demultiplexing Is added. For example, in the case of TCP / IP which is a general-purpose interface, IPv4 (0X0800), ARP (0X0806), and the like can enter here, and a unique code for synchronous communication can also be inserted. The data field contains a packet of IPv4 (example in the figure) or ARP protocol.

  In the above configuration, as shown in FIG. 8A, when synchronous packets 601, 603,... Are sequentially input from the communication cable 330 to the lower communication I / F unit 432 of the slave communication controller 430, The packet 601 enters the lower-level communication I / F unit 432 from the input port, is parallelized, and is input to the synchronous / asynchronous identification unit 440.

  Since the synchronous communication packet is for a dedicated line, an ID that is not allocated to the general-purpose interface is added to the type field. Therefore, the synchronous / asynchronous identifying unit 440 identifies synchronous communication by identifying the upper layer protocol of the type field. Whether the packet is an asynchronous communication packet can be identified.

  If the communication packet 601 is determined to be a synchronous communication packet, the communication packet 601 is directly input to the upper communication I / F unit 438 via the line setting unit 436, serialized, and output to the output port.

  Thereafter, the synchronization packet 602 generated in the local station, which is input from the access control unit 434, is input to the higher-level communication I / F unit 438 via the line setting unit 436, serialized, and output to the output port. In the state of FIG. 8A, the communication packets 601 and 602 are both synchronous communication packets and are synchronized with each other, and thus do not collide.

  Next, as shown in FIG. 8B, there is a possibility that the synchronous communication packet 602 entering the access control unit 434 from the own station and the asynchronous communication packet 605 entering the lower-layer communication I / F unit 432 from another station may collide. If there is no communication packet 605, the communication packet 605 enters the lower-layer communication I / F unit 432 from the input port, is parallelized, and then input to the synchronous / asynchronous identification unit 440. When the communication packet 605 is determined to be an asynchronous communication packet, the packet is input to the packet arbitration unit 442. The packet arbitration unit 442 obtains timing information from the access control unit 434 and obtains full length information from the header part of the upper layer protocol of the communication packet 605 and collides with the synchronous communication packet 604 output from the access control unit 434. Determine the possibility. If it is determined that a sufficient gap with the synchronous communication packet 604 can be secured (no collision), it is directly input to the higher-level communication I / F unit 438 via the line setting unit 436, serialized, and output to the output port. Thereafter, the synchronous communication packet 604 from the access control unit 434 is input to the higher-level communication I / F unit 438 via the line setting unit 436, serialized, and output to the output port.

  Next, as shown in FIG. 8C, when the asynchronous communication packet 606 is input to the input port of the lower-level communication I / F unit 432 and the synchronous communication packet 602 from the access control unit 434 may collide. The communication packet 606 enters the lower-layer communication I / F unit 432 from the input port, is parallelized, and is input to the synchronous / asynchronous identification unit 440. When the communication packet 606 is determined to be an asynchronous communication packet, the packet is input to the packet arbitration unit 442. The packet arbitration unit 442 obtains timing information from the access control unit 434 and also obtains full length information from the header part of the upper layer protocol of the communication packet 606, and the synchronous communication packet 602 output from the access control unit 434 collides. Determine the possibility. When it is determined that there is a collision, the communication packet 606 is temporarily stored in the buffer unit 444, and the synchronous communication packet 602 from the access control unit 434 is input to the higher-level communication I / F unit 438 via the line setting unit 436. After being serialized and output to the output port, the communication packet 606 is read from the buffer unit 444, input to the higher-level communication I / F unit 438 via the line setting unit 436, serialized, and output to the output port. . In the state of FIG. 8C, the communication packet 606 is output after outputting the synchronous communication packet 602, so that it does not collide.

  The master communication controller 410 shown in FIG. 5 is also similar between the synchronous communication packet output from the access control unit 416 and the asynchronous communication packet input from the sensor or camera to the communication I / F unit 420. The synchronous communication packet output from the access control unit 416 and the asynchronous communication packet input from the communication I / F unit 420 do not collide with each other.

  In the above-described embodiment, the communication interface is Ethernet (registered trademark). However, the type of the communication interface is not limited to this, and the present invention can be realized as another interface. Also, the types of peripheral devices are not limited to motor drive devices, sensors, cameras, and the like. Further, the frame format is not limited to the example shown in FIG.

Block diagram showing a configuration example of a conventional FA network system Block diagram showing an example of a conventional master communication controller Similarly, a block diagram showing a configuration of a slave communication controller The block diagram which shows the structure of embodiment of FA network system which concerns on this invention The block diagram which shows the structure of the master communication controller used by the said embodiment. The block diagram which similarly shows the constitution of the slave communication controller The figure which shows an example of the frame format of the serial communication system used by the said embodiment Time chart for explaining the operation of the embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... High-order control apparatus 200 ... Servo motor 210 ... Motor drive device 220 ... Sensor 230 ... Camera 330 ... Communication cable 410 ... Master communication controller 422, 442 ... Packet arbitration part 424, 444 ... Buffer part 440 ... Synchronous / asynchronous identification part

Claims (1)

In a serial communication device for performing synchronous communication and asynchronous communication via the same serial communication path between a plurality of peripheral devices and a control device using a communication packet,
A communication packet including header information capable of identifying synchronous communication and asynchronous communication;
Means for detecting a possibility of collision between a synchronous communication packet transmitted from the own station and an asynchronous communication packet input from another peripheral device;
A communication packet waiting buffer provided at the input port;
When a synchronous communication packet is received, the synchronous communication packet is output as it is. When an asynchronous communication packet is received, if an occurrence of a collision with the synchronous communication packet transmitted from the local station is expected, the asynchronous communication packet buffer Means for preferentially transmitting synchronous communication packets by ringing;
When it is determined that there is no collision, a means for outputting the asynchronous communication packet as it is,
A serial communication device comprising:

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