Siemens SINAMICS V20 Operating Instructions Manual page 178

Communicating with the PLC
7.1 USS communication
The messages are always sent in the following format (half-duplex communication):
● Response delay time: 20 ms
● Start delay time: depends on baud rate (minimum operation time for 2-character string:
0.12 to 2.3 ms)
● Message transfer sequence:
– master polls slave 1, then slave 1 responds
– master polls slave 2, then slave 2 responds
● Fixed framing characters that cannot be altered:
– 8 data bits
– 1 parity bit
– 1 or 2 stop bits
Abbreviation
STX
LGE
ADR
1. ...... n.
BCC
Request and response IDs
Request and response IDs are written in bits 12 to 15 of the PKW (parameter ID value) part
of USS telegram.
Request IDs (master → slave)
Request ID Description
0 No request
1 Request parameter value
2 Modify parameter value (word)
3 Modify parameter value (double word)
176
Significance Length
Start of text ASCII characters
Telegram length 1 byte
Address 1 byte
Net characters Each 1 byte
Block check character 1 byte
Explanation
02 hex
Contains the telegram length
Contains the slave address and the
telegram type (binary coded)
Net data, contents are dependent on the
request
Data security characters
Response ID
positive
0
1/2
1
2
SINAMICS V20 Converter
Operating Instructions, 10/2019, A5E34559884-012
negative
7/8
7/8
7/8
7/8