Communication processor and Modbus TCP
13.5 Modbus communication
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
1191
As of version V4.1 of the S7-1200 CPU together with STEP 7 V13 SP1, the CPU extends the
capability of Modbus RTU to use a PROFINET or PROFIBUS distributed I/O rack to
communicate to various devices (RFID readers, GPS device, and others):
● PROFINET (Page 804): You connect the Ethernet interface of the S7-1200 CPU to a
PROFINET interface module. PtP communication modules in the rack with the interface
module can then provide serial communications to the PtP devices.
● PROFIBUS (Page 968): You insert a PROFIBUS communication module in the left side
of the rack with the S7-1200 CPU. You connect the PROFIBUS communication module
to a rack containing a PROFIBUS interface module. PtP communication modules in the
rack with the interface module can then provide serial communications to the PtP
devices.
For this reason, the S7-1200 supports two sets of PtP instructions:
● Legacy Modbus RTU instructions (Page 1270): These Modbus RTU instructions existed
prior to version V4.0 of the S7-1200 and only work with serial communications using a
CM 1241 communication module or CB 1241 communication board.
● Modbus RTU instructions (Page 1194): These Modbus RTU instructions provide all of the
functionality of the legacy instructions, plus the ability to connect to PROFINET and
PROFIBUS distributed I/O. These Modbus RTU instructions allow you to configure the
communications between the PtP communication modules in the distributed I/O rack and
the PtP devices. S7-1200 CM 1241 modules must have a minimum firmware version of
V2.1 to use these Modbus RTU instructions.
To Next Page
Loading...
