Communication processor and Modbus TCP
13.7 Legacy USS communication (CM/CB 1241 only)
S7-1200 Programmable controller
1234 System Manual, V4.2, 09/2016, A5E02486680-AK
Table 13- 117 Condition codes
CM or CB is RS485 and no signals can be set
80F1 Signals cannot be set because of Hardware flow control
Cannot set DSR because module is DTE
80F3 Cannot set DTR because module is DCE
Legacy USS communication (CM/CB 1241 only)
The USS instructions control the operation of motor drives which support the universal serial
interface (USS) protocol. You can use the USS instructions to communicate with multiple
drives through RS485 connections to CM 1241 RS485 communication modules or a CB
1241 RS485 communication board. Up to three CM 1241 RS422/RS485 modules and one
CB 1241 RS485 board can be installed in a S7-1200 CPU. Each RS485 port can operate up
to sixteen drives.
The USS protocol uses a master-slave network for communications over a serial bus. The
master uses an address parameter to send a message to a selected slave. A slave itself can
never transmit without first receiving a request to do so. Direct message transfer between
the individual slaves is not possible. USS communication operates in half-duplex mode. The
following USS illustration shows a network diagram for an example drive application.
To Next Page
Loading...
