Ptp, Uss, And Modbus Communication Protocols; Using The Rs232 And Rs485 Communication Interfaces - Siemens SIMATIC S7-1200 Manual

7.10

PtP, USS, and Modbus communication protocols

The CPU supports the PtP protocol for character-based serial communication, in which the
user application completely defines and implements the protocol of choice.
PtP is serial communication that supports a variety of baud rates and parity options. STEP 7
provides instructions for the USS drive protocol (RS485 only) and Modbus RTU Master and
RTU Slave protocols.
7.10.1

Using the RS232 and RS485 communication interfaces

Three communication modules (CMs) and one communication board (CB) provide the
interface for PtP communications:
● CM 1241 RS232
● CM 1241 RS485
● CM 1241 RS422/485
● CB 1241 RS485
You can connect up to three CMs (of any type) plus a CB for a total of four communication
interfaces. Install the CM to the left of the CPU or another CM. Install the CB on the front of
the CPU. Refer to the "Installation" chapter for detailed instructions on module installation
and removal.
The RS232 and RS485 communication interfaces have the following characteristics:
● Have an isolated port
● Support Point-to-Point protocols
● Are configured and programmed through extended instructions and library functions
● Display transmit and receive activity by means of LEDs
● Display a diagnostic LED (CMs only)
● Are powered by the CPU: No external power connection is needed.
Refer to the technical specifications for communication interfaces.
Easy Book
Manual, 11/2011, A5E02486774-04
Easy to communicate between devices
7.10 PtP, USS, and Modbus communication protocols
PtP enables a wide variety of possibilities:
 Sending information directly to an external
device such as a printer
 Receiving information from devices such as
barcode readers, RFID readers, third-party
camera or vision systems, and many other
types of devices
 Sending and receiving data with devices such
as GPS devices, third-party camera or vision
systems, or radio modems
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