Siemens SIMATIC S7-300 Reference Manual page 62

Basic instructions
MODBUS slave (RTU)
✔ ✔
Modbus slave instruction for CP 341
✔ ✔
Modbus slave instruction for CP 441
MODBUS: CP 443
✔ ✔
Establish communication between
a CP and a partner that supports the
OPEN MODBUS/TCP protocol
✔ ✔
Communicate as Modbus client
✔ ✔
Communicate as Modbus server
ET 200S serial interface
✔ ✔ ✔
Receive data
✔ ✔ ✔
Send data
✔ ✔ ✔
Read accompanying signals on the RS-232C
interface
✔ ✔ ✔
Write accompanying signals on the RS-232C
interface
✔ ✔ ✔
Set data flow control using XON/XOFF
✔ ✔ ✔
Set data flow control using RTS/CTS
A5E33285102-AB
Extended instructions
Description
Technology
STL
LAD / FBD
(not S7-1200)
MODB_341
MODB_441
MODBUSCP
MB_CPCLI
MB_CPSRV
Note: S stands for serial
S_RCV
S_SEND
S_VSTAT
S_VSET
S_XON
S_RTS
Communication
SCL
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