Transmit And Receive (Freeport On Rs485/Rs232) - Siemens SIMATIC S7 System Manual

7.3.2

Transmit and receive (Freeport on RS485/RS232)

You can use the Transmit (XMT) and Receive (RCV) instructions for communication
between a S7-200 SMART CPU and other devices through the CPU serial port(s). Each
S7-200 SMART CPU provides an integrated RS485 port (Port 0). The standard CPUs
additionally support an optional CM01 Signal Board (SB) RS232/RS485 port (Port 1). The
communication protocol must be implemented in the user program.
Note
The CPU models CPU CR20s, CPU CR30s, CPU CR40s, and CPU CR60s do not support
the use of signal boards.
LAD / FBD STL
XMT
RCV
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Description
TBL, PORT
The Transmit instruction (XMT) is used in Freeport mode to transmit data
by means of the communications port(s).
TBL, PORT
The Receive instruction (RCV) initiates or terminates the receive message
function. You must specify a start and an end condition for the Receive
box to operate. Messages received through the specified port (PORT) are
stored in the data buffer (TBL). The first entry in the data buffer specifies
the number of bytes received.
Program instructions
7.3 Communication
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