User Manual

Easy to communicate between devices
7.10 PtP, USS, and Modbus communication protocols
Easy Book
Manual, 03/2014, A5E02486774-AF
163
7.10
PtP, USS, and Modbus communication protocols
7.10.1
Point-to-point communication
The CPU supports the following Point-to-Point communication (PtP) for character-based
serial protocols:
● PtP (Page 164)
● USS (Page 165)
● Modbus (Page 167)
PtP provides maximum freedom and flexibility, but requires extensive implementation in the
user program.
PtP enables a wide var
iety of possibilities:
•
The ability to send information directly to an external
device such as a printer
•
The ability to receive information from other devices
such as barcode readers, RFID readers, third-party
camera or vision systems, and many other types of
devices
•
The ability to exchange information, sending and
receiving data, with other devices such as GPS
devices, third-party camera or vision systems, radio
modems, and many more
This type of PtP communication is serial
communication that uses standard
UARTs to support a
variety of baud rates and parity options. The RS232
and RS422/485 communication modules (CM
1241)
and the RS485 communication board (CB
1241)
provide the electrical interfaces for performing the PtP
communications.
7.10.2
Using the serial communication interfaces
Two communication modules (CMs) and one communication board (CB) provide the
interface for PtP communications:
● CM 1241 RS232
● 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 in the S7-1200 System Manual for detailed
instructions on module installation and removal.