Siemens SINAMICS S110 - General Information about Communication with USS over RS485; Structure of a USS Telegram

Communication
9.5 Communication using USS
Function Manual
642 Function Manual, 01/2011, 6SL3097-4AB10-0BP3
9.5.3 General information about communication with USS over RS485
General information
Communication using the USS protocol takes place over the RS485 interface with a
maximum of 31 slaves. The following character frame applies for the USS telegram:
ELWVRIGDWD
%LW
VWRS
%LW
3HYHQ
%LW
6WDUW
For information about connection, please refer to the Equipment Manual.
9.5.4 Structure of a USS telegram
Description
The structure of a typical USS telegram is shown in the figure below.
6WDUWGHOD\ 866IUDPH
n net data
Final
information
Header information
ELWGDWD
%LW
VWRS
%LW
3HYHQ
%LW
6WDUW
STX LGE ADR 1. 2. : : : n BCC
Figure 9-48 Structure of a USS telegram
Telegrams with both a variable and fixed length can be used. This can be selected using
parameters p2022 and p2023 to define the length of the PZD and the PKW.
The most common application using a fixed length is shown below:
STX 1 byte
LGE 1 byte
ADR 1 byte
PKW 8 bytes (4 words: PKE + IND + PWE1 + PWE2) Net data
PZD 4 bytes (2 words: PZD1 + PZD2)
BCC 1 byte
Total: 16 bytes (LGE indicates 14 bytes, because STX and LGE were not counted
in LGE)