Requirements For Using The Uss Protocol - Siemens SIMATIC S7-1200 System Manual

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Communication processor and Modbus TCP

13.4 Universal serial interface (USS) communication

Requirements for using the USS protocol

The four USS instructions use two function blocks (FBs) and two functions (FCs) to support

the USS protocol. One USS_Port_Scan instance data block (DB) is used for each USS

network. The USS_Port_Scan instance data block contains temporary storage and buffers

for all drives on that USS network. The USS instructions share the information in this data

All drives (up to 16) connected to a single RS485 port are part of the same USS network. All

drives connected to a different RS485 port are part of a different USS network. Each USS

network is managed using a unique data block. All instructions associated with a single USS

network must share this data block. This includes all USS_Drive_Control, USS_Port_Scan,

USS_Read_Param, and USS_Write_Param instructions used to control all drives on a single

USS network.

The USS_Drive_Control instruction is a Function Block (FB). When you place the

USS_Drive_Control instruction into the program editor, you will be prompted by the "Call

options" dialog to assign a DB for this FB. If this is the first USS_Drive_Control instruction in

this program for this USS network, then you can accept the default DB assignment (or

change the name if you wish) and the new DB is created for you. If however this is not the

first USS_Drive_Control instruction for this channel, then you must use the drop-down list in

the "Call options" dialog to select the DB name that was previously assigned for this USS

S7-1200 Programmable controller

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