Siemens SINAMICS G120 CU240E-2 - Structure of a USS Telegram

Connection to a fieldbus
6.4 Communication via RS485
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
133
6.4.2.2 Structure of a USS telegram
A USS telegram comprises a sequence of characters, which are sent in a defined sequence.
The sequence of characters of a USS telegram is shown in the following diagram.
6WDUWGHOD\ 866IUDPH
n net data
Final
information
Header information
: : : BCCn2ADRLGESTX
1.
Figure 6-12 Structure of a USS telegram
Every character within the telegram comprises 11 bits.
ELWVRIGDWD
%LW
VWRS
%LW
3HYHQ
%LW
6WDUW
Description
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 within the net
data.
STX 1 byte
LGE 1 byte
ADR 1 byte
PKW 8 bytes (4 words: PKE + IND + PWE1 + PWE2) Net data
(example)
PZD 4 bytes (2 words: PZD1 + PZD2)
BCC 1 byte
Start delay
The start delay must be maintained before a new master telegram is started.
STX
The STX block is an ASCII character (0x02) and indicates the beginning of a message.