Principle Of Operation; Complete Overview; Basic Software Structure; Implementation With Simatic S7-1200 - Siemens SINAMICS V20 Manual

3 Principle of Operation

3.1 Complete overview

Principle of Operation
3
3.1 Complete overview
3.1.1

Basic software structure

The USS protocol uses a master/slave network for communication via a serial bus.
The master (SIMATIC controller) uses an address parameter to send a message to
a selected slave (SINAMICS V20). A slave cannot send without having received a
request for sending. Direct information transmission between the individual slaves
is not possible. USS communication takes place in half duplex operation.
In STEP 7, different libraries have to be used for the S7-1200 and S7-1500
controllers. However, their system blocks are handled similarly.
The STEP 7 program is divided into an interrupt-driven part and a program part to
be cyclically processed.
Interrupt-driven part
This part calls a USS_PORT (S7-1200) or USS-Port_Scan (S7-1500) system
instruction from a cyclic interrupt OB for each communication port. This system
instruction processes communication via the USS network.
Cyclic part
This part calls a USS_DRV (S7-1200) or USS_Drive_Control (S7-1500) system
instruction on the respective port from a cycle OB for each existing slave. This
system instruction prepares send data for the drive and evaluates the drive's
response data.
3.1.2

Implementation with SIMATIC S7-1200

Use the following system instructions:

USS_PORT
to process communication via the USS

USS_DRV
to prepare the send data and evaluate the response data
These system instructions can be found in the Instructions task card,
Communication.
SINAMICS V20 at S7-1200/1500 via USS
Entry ID: 109480894, V1.0, 09/2018
®
network
10