Legacy Uss Communication (Cm/Cb 1241 Only) - Siemens SIMATIC S7-1200 System Manual

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Communication processor and Modbus TCP

13.7 Legacy USS communication (CM/CB 1241 only)

Table 13- 117 Condition codes

STATUS (W#16#....)

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.

CM or CB is RS485 and no signals can be set

Signals cannot be set because of Hardware flow control

Cannot set DSR because module is DTE

Cannot set DTR because module is DCE

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK