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

105BCommunication processor
12.4 Universal serial interface (USS) communication
12.4.1

Requirements for using the USS protocol

The four USS instructions use 1 FB and 3 FCs to support the USS protocol. One
USS_PORT instance data block (DB) is used for each USS network. The USS_PORT
instance data block contains temporary storage and buffers for all drives on that USS
network. The USS instructions share the information in this data block.
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_DRV, USS_PORT, USS_RPM,
and USS_WPM instructions used to control all drives on a single USS network.
The USS_DRV instruction is a Function Block (FB). When you place the USS_DRV
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_DRV 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_DRV 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 network.
Instructions USS_PORT, USS_RPM, and USS_WPM are all Functions (FCs). No DB is
assigned when you place these FCs in the editor. Instead, you must assign the appropriate
DB reference to the "USS_DB" input of these instructions. Double-click on the parameter
field and then click on the parameter helper icon to see the available DB names).
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S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05