MSI communication between S7-200 and S7-300 - Database & Sql Blog Articles

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MPI (Multipoint Interface) is a communication protocol used internally by Siemens, and the physical layer is RS-485. Through the S7 basic communication of the MPI network, the S7-300 can read and write the storage area of ​​the S7-200 with the system functions X_GET and X_PUT, and can read and write 76 bytes of data at most. The S7-200 does not need to write a communication program. The advantage is that the RS-485 communication interface that comes with plc does not need to increase the hardware for communication, and the programming is simple and easy to implement.

1. Communication parameter setting

The station address of the CPU 224 in the MPI network is set to 3 by the system block. For ease of download and monitoring, the communication rates of the S7-200, S7-300, and computer are all set to 19.2 kbit/s. The system block needs to be downloaded to the CPU and the set parameters will take effect.

When configuring, connect the CPU 315-2DP to the MPI network and set the MPI station address to 2. Download the set parameters to the CPU 315-2DP.

The SFC 68 "X_PUT" is called in the OB 35 of the CPU 315-2DP, and the 76-byte data of the DB 1 of the own station is transmitted to the DBB 100 to DBB 175 of the DB 1 of the communication partner, that is, VB 100 to VB 175 of the CPU 224. The SFC 67 "X_GET" is called, and the data in the VB200 to VB275 of the CPU 224 (i.e., DBB200 to DBB275 of the DB 1) is read and stored in the DB 2. The time interval for executing OB35 is the default 100ms.

The following is the program of the cyclic interrupt organization block OB35 of the CPU 315-2DP:

Block 1: Write the data in DB1 of the station to the #p# page header #e#V area of ​​the CPU 224

CALL "X_PUT"

REQ :=TRUE

CONT :=TRUE

DEST_ID :=W#16#3 //The MPI address of the S7-200

VAR_ADDR:=P#DB1.DBX100.0 BYTE 76 //S7-200 to write data to VB100~VB175

SD :=P#DB1.DBX0.0 BYTE 76 //Store the address area of ​​the data to be sent by this station

RET_VAL:=MW2

BUSY :=M0.1

Block 2: Read the data of the V area of ​​the CPU 224 and save it to the DB 2 of the station.

CALL "X_GET"

REQ :=TRUE

CONT :=TRUE

DEST_ID :=W#16#3

_{#p#Page title#e#} VAR_ADDR:= P#DB1.DBX200.0 BYTE 76 //To read VB200～VB275 of S7-200

RET_VAL :=MW4

BUSY :=M0.3

RD := P#DB2.DBX0.0 BYTE 76 //Save the address area of ​​the read data

In order to verify whether the communication is realized, the word of the 76-byte data transmission area of ​​the data block DB 1 is preset to W#16#3333 in the initialization program OB100, and the 76-byte data reception area of ​​the DB 2 is reset to 0.

In order to verify whether the communication is realized, in the OB1 of the CPU 224, the transmission data areas VW204 to VW274 are preset to 16#2222 in the first scanning period, and the reception data areas VW100 to VW174 are cleared.

LD SM0.1

FILL #p#分页头#e#16#2222, VW204, 38

FILL 16#0, VW100, 38

The memory area participating in the communication can be monitored by the variable table of the CPU 315-2DP and the status table of the CPU 224.

When I first experimented, I succeeded very smoothly. The general feeling is that communication is easy to implement as long as there is no problem with configuration and programming.