JP2001251319A - Communication system and data transmission method for the communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system where a slave station can respond to a data request from a master station in real time without increasing a transmission rate and a transmission cycle and to provide a data transmission method for the communication system. SOLUTION: A CPU 13i of an i-th slave station 11i sequentially writes data to be returned to a master station 101 in advance to a RAM 16i in a transmission section 12i by types, a discrimination section 15i in the transmission section 12i discriminates types of data to be returned to the master station 101 in response to a return command from the master station 101, refers to a table TAB storing storage addresses of the RAM 16i by types of the returned data, reads the returned data of a concerned type stored in the RAM 16i and returns the data to the master station 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for performing cyclic serial communication between a master station and a plurality of slave stations, and a data transmission method of the communication system. The present invention relates to a communication system in which a slave station can respond in real time to a data request from a master station without speeding up, and a data transmission method of the communication system.

[0002]

2. Description of the Related Art FIG. 4 is a configuration diagram of a communication system applied to a conventional FA system and the like. In the figure, 401 is a master station, 41i (i = 1 to N) is a slave station, and the master station 401 and N slave stations 411 to 41N are connected in a one-to-N multi-drop connection by a half-duplex transmission line. It is. FIG. 4 representatively shows the configuration of the i-th slave station 41i, and the i-th slave station 41i includes an R buffer including a reception buffer RXB 'and a transmission buffer TXB' therein.
The configuration includes an AM 46i, a transmission unit 42i for performing data transmission with the master station 401, and a CPU 43i. FIG. 5 illustrates a memory map of the reception buffer RXB 'and the transmission buffer TXB' of the RAM 46i. For example, when the conventional communication system is applied to a servo control system, the slave stations 411 to 41
The operation of each of the lower controllers N is controlled by data sent from the upper controller as the master station 401. That is, the master station 401 (upper controller)
A command is sent to the slave stations 411 to 41N (lower-level controllers) via a transmission path to request necessary data. Representatively, the operation of data transmission in the i-th slave station 41i will be described. First, the transmission unit 42i receives the data transmitted from the master station 401,
Write to the receive buffer RXB 'in i. Next, CPU
Reference numeral 43i reads the received data, specifically, the operation command, the return command, and the command data from the reception buffer RXB ', and determines what the data requested by the master station 401 is based on the return command. Here, when the slave stations 411 to 41N are network-compatible servos, the data requested to be returned by the master station 401 usually includes
Current value data, deviation value data, torque data and I /
There is O data and the like. Further, in accordance with the determination based on the return instruction, the CPU 43i writes the return data requested by the master station 401 and the return content indicating the attribute of the return data to the transmission buffer TXB 'in the RAM 42i. Then, the transmission unit 42i reads out the contents of the transmission buffer TXB 'in the RAM 42i, that is, the status display, the return contents, and the return data, and transmits them to the master station 401 via the transmission path. As described above, in the cyclic serial communication performed through the half-duplex transmission line, when the master station 401 periodically sends command data to each of the slave stations 411 to 41N, each slave station 41i ( i-
In 1-N), the data prepared in advance by the transmission unit 42i is read from the RAM 42i and returned. This is because the transmission speed and the transmission cycle are particularly short in a communication system applied to an FA system or the like, so that the data transmitted by the master station 401 is transmitted to the CP of the slave station 41i.
This is because there is no time for the U43i to prepare the return data in the transmission cycle, and there is no choice but to return to the master station 401 in the next transmission cycle.

[0003]

As described above, in the above-mentioned conventional communication system and the data transmission method of the communication system, in the slave station, after the CPU finishes the reception processing, the master station makes a request. Since the data is determined and written to the transmission buffer in the RAM and then transmitted to the master station, the data is surely delayed for at least one cycle in the cyclic serial communication. In particular, it was a problem. As one method of increasing the speed in a transmission system such as an FA system, there is a method of increasing the transmission rate (clock frequency), but there is a disadvantage that a new problem such as EMC occurs. The present invention has been made in view of the above-mentioned conventional circumstances and problems, and enables a slave station to respond in real time to a data request from a master station without further increasing a transmission speed or a transmission cycle. An object of the present invention is to provide a communication system and a data transmission method of the communication system.

[0004]

According to a first aspect of the present invention, there is provided a communication system for performing a cyclic serial communication between a master station and a plurality of slave stations. A plurality of slave stations, storage means for holding return data for each type, a table for holding storage addresses of the storage means for each type of return data, and the master station in response to a command from the master station. Determine the type of the return data to be returned to, referring to the table, read the return data of the corresponding type held in the storage means, and a transmission means comprising a determination means for returning to the master station, Control means for sequentially writing data to be returned to the master station to the storage means of the transmission means. A data transmission method for a communication system according to claim 2 is a data transmission method for a communication system in which a master station and a plurality of slave stations perform cyclic serial communication, wherein the slave station returns to the master station. A writing step of sequentially writing data to be stored in the storage means for each type; a determining step of determining the type of return data to be returned by the slave station to the master station in response to a command from the master station; Referring to a table holding the storage addresses of the storage means for each type, reading back the return data of the corresponding type held in the storage means and returning the data to the master station. is there.

In the data transmission method of the communication system according to claim 1 and the communication system according to claim 2,
In the writing step, the data to be returned to the master station is sequentially written in the storage means in the transmission means for each type by the control means of the slave station in advance, and the judgment means in the transmission means performs the judgment step from the master station in the judgment step. The type of the return data to be returned to the master station is determined in accordance with the command, and the return step refers to a table holding the storage address of the storage unit for each type of the return data and stores the return address in the storage unit. The return data of the corresponding type is read and returned to the master station. As described above, the determination means in the transmission means determines the type of the return data based on the instruction from the master station, and directly accesses the storage means to return the data to the master station. Since data can be returned without waiting for processing by the CPU after the processing is completed, data can be returned in a transmission cycle requested by the master station without causing a data delay of one cycle in cyclic serial communication. As a result, the slave station can respond in real time to a data request from the master station without increasing the transmission speed or transmission cycle.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a communication system and a data transmission method of the communication system according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a communication system according to an embodiment of the present invention. FIG. 1A is an overall configuration diagram of the communication system, and FIG.
It is a block diagram of a slave station. In FIG. 1, the communication system of the present embodiment includes a master station 101 and N slave stations (first slave station 111,..., I-th slave station 11i,
.., Nth slave station 11N) via a communication cable to connect the master station 101 to the N slave stations 111 to 11N.
Is a one-to-N multi-drop communication system that performs communication with the STA according to, for example, an HDLC procedure. When the communication system according to the present embodiment is applied to, for example, a control system for a servomotor, each of the servos (lower-level controllers) serving as the slave stations 111 to 11N operates based on data transmitted from a control unit (upper-level controller) serving as the master station 101. It will be controlled. Although not shown, the master station 101 has a configuration including, for example, a CPU, a transmission data buffer, a reception data buffer, and a transmission / reception unit. Also,
As shown in FIG. 1B, each of the slave stations 111 to 11N typically has an i-th slave station 11i (i = 1 to 1).
N) is a judgment unit 15i and a RAM (storage means) 16i
And a CPU (control means) 13i. Here, the RAM 16i includes a reception buffer RXB and a transmission buffer TXB.
The memory map of the reception buffer RXB is the same as that of the communication system of the conventional example (see FIG. 5), but the memory map of the transmission buffer TXB has a feature unique to the communication system of the present embodiment. That is, the transmission buffer TXB
Has a storage area for storing return data to the master station 101 for each type, and a table TAB for storing storage addresses for each type of return data. In the present embodiment, the i-th
It is assumed that the slave station 11i is a network-compatible servo, and the current value data GDT, the deviation value data HDT, the torque data TDT, and the I / O data IO are used as return data for each type that is always requested to be returned from the master station 101.
D is illustrated. The determination unit 15i determines the type of return data to be returned to the master station 101 in response to a return command from the master station 101, and refers to the table TAB to determine the RA
The return data of the corresponding type stored in M16i is read and returned to the master station 101. CPU 13i
Writes the data to be returned to the master station 101 sequentially to the RAM 16i of the transmission unit 12i.

Next, in the communication system of the present embodiment having the above configuration, the master station 101 and N
Communication between the slave stations 111 to 11N
A brief description is given with reference to FIG. FIG. 2 is an explanatory diagram illustrating communication between the master station 101 and the N slave stations 111 to 11N in the communication system according to the present embodiment.
In synchronous communication data transmission in an FA system, etc., the maximum number of slave stations N is fixed, the number of bytes of transmission data is fixed, and normal communication is performed by cyclic transmission with a constant master transmission cycle and communication cycle. Have been done. Further, the transmission line in the communication system of the present embodiment is a half-duplex bidirectional transmission line, and in FIG.
, The lower side represents the slave stations 111 to 11N, respectively.
Tx1 to TxN represent transmission data from the master station 101,
Rx1 to RxN indicate response data from the slave stations 111 to 11N, respectively. Here, as shown in Rx3, each transmission data has a configuration according to the frame format of the HDLC procedure, that is, a start flag F, an address part AD, a control part COM, an information part DATA, a frame check sequence CRC, and an end flag. F is provided. In the cyclic serial communication performed through such a half-duplex transmission path, command data is periodically sent from the master station 101 to each of the slave stations 111 to 11N. 11i (i = 1 to 1
In N), the data requested by the master station 101 is returned as follows. FIG. 3 is an explanatory diagram schematically illustrating a data transmission method in the communication system according to the present embodiment. The CPU 13i of the i-th slave station 11i always stores various data requested to be returned from the master station 101, that is, current value data GDT, deviation value data HDT, torque data TDT, and I / O data IOD in a predetermined storage area of the RAM 16i. They are stored sequentially. Here, the head address of various data in the RAM 16i is the RAM 16i.
Is written in advance in the table TAB of the
i is stored in the RAM 16i by referring to the table TAB.
It is possible to directly access various storage areas by accessing a predetermined storage area. That is, when a return command is transmitted from the master station 101 to the i-th slave station 11i,
The determination unit 15i in the transmission unit 12i determines the type of data to be returned to the master station 101 based on the return command, and issues a transmission command to the table TAB in the RAM 16i, thereby transmitting the data in the predetermined storage area in the RAM 16i. Directly access various data (current value data GDT, deviation value data HDT, torque data TDT or I / O data IOD), switch and output transmission data, and transmit
The data is returned to the master station 101 via a transmitting / receiving unit (not shown) in 2i.

As described above, according to the communication system and the data transmission method of the communication system of the present embodiment,
(In the writing step) i-th slave station 1
The data to be returned to the master station 101 is sequentially written into the RAM 16i in the transmission unit 12i for each type by the CPU 13i of the transmission unit 12i. The type of the return data to be returned to the master station 101 is determined in response to the return instruction, and the RAM 16i is referred to a table TAB holding the storage address of the RAM 16i for each type of return data (by the return step). The held return data of the corresponding type is read out and returned to the master station 101. As described above, the determination unit 15i in the transmission unit 12i determines the type of the return data based on the command from the master station 101 and directly accesses the RAM 16i to return the data to the master station 101. CPU 13i after reception processing of station 11i
Therefore, the data can be returned in the transmission cycle requested by the master station 101 without causing a data delay of one cycle in the cyclic serial communication. As a result, the slave station 11i can respond in real time to a data request from the master station 101 without increasing the transmission speed or transmission cycle.

[0009]

As described above, according to the communication system and the data transmission method of the communication system of the present invention, in the writing step, the data to be returned to the master station is previously stored in the transmission means by the control means of the slave station. Is sequentially written in the storage means for each type, and the determination means in the transmission means determines the type of return data to be returned to the master station in response to a command from the master station in a determination step,
The return step refers to a table holding the storage addresses of the storage means for each type of return data, reads out the return data of the corresponding type stored in the storage means, and returns the read data to the master station. The determination means in the step (1) determines the type of the return data based on the command from the master station, and directly accesses the storage means to return the data to the master station. Therefore, one cycle of data delay in cyclic serial communication. Data can be returned in the transmission cycle requested by the master station without causing a problem.As a result, the slave station responds to the data request from the master station in real time without increasing the transmission speed or transmission cycle. A possible communication system and a data transmission method of the communication system can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a communication system according to an embodiment of the present invention. FIG. 1A is a general configuration diagram of a communication system, and FIG. 1B is a configuration diagram of an i-th slave station.

FIG. 2 is an explanatory diagram illustrating communication between a master station and N slave stations in the communication system of the embodiment.

FIG. 3 is an explanatory diagram schematically illustrating a data transmission method in the communication system according to the embodiment.

FIG. 4 is a configuration diagram of a conventional communication system.

FIG. 5 is an explanatory diagram illustrating a memory map of a RAM of a conventional communication system.

[Explanation of symbols]

 101, 401 Master station 111-11N, 411-41N Slave station 11i i-th slave station 12i, 42i Transmission unit (transmission unit) 13i, 43i CPU (control unit) 15i Judgment unit (judgment unit) 16i, 46i RAM (storage unit) RXB, RXB 'Receive buffer TXB' Transmission buffer GDT Current value data HDT Deviation data TDT Torque data IOD I / O data TAB table

Continued on the front page F-term (reference)

Claims (2)

[Claims] 1. A communication system for performing cyclic serial communication between a master station and a plurality of slave stations, the plurality of slave stations comprising: storage means for holding return data for each type; A table that stores the storage address of the storage unit for each, and determines the type of return data to be returned to the master station in response to a command from the master station, and refers to the table and is stored in the storage unit. Determining means for reading the return data of the corresponding type and returning the read data to the master station;
And a control unit for sequentially writing data to be returned to the master station to a storage unit of the transmission unit. 2. A data transmission method for a communication system for performing cyclic serial communication between a master station and a plurality of slave stations, wherein data to be returned by the slave station to the master station is stored in storage means for each type. A writing step for sequentially writing, a judging step of judging a type of return data to be returned to the master station by the slave station in response to a command from the master station, and a storage address of the storage means for each type of return data. A data transmission method for a communication system, comprising: reading a return data of a corresponding type stored in the storage unit with reference to the stored table, and returning the read data to the master station.