Telegram Structure - Siemens Sinamics G120P Operating Instructions Manual

Operation
6.8 Communication via RS485
6.8.2.2

Telegram structure

Overview
A USS telegram comprises a series of elements with a defined sequence. Each element
contains 11 bits.
Figure 6-13
Telegram part
Start delay / re-
sponse delay
STX
LGE
ADR
Net data
BCC
220
Structure of a USS telegram
Description
There is always a start and/or response delay between two telegrams (see
alsoTime-out and other errors (Page 227)).
An ASCII character (02 hex) indicates the beginning of the message.
The telegram length "LGE" is calculated as follows:
LGE = user data (n bytes) + ADR (1 byte) + BCC (1 byte)
Bit 7 = 0: Normal data exchange.
•
Bit 7 = 1: To transfer telegrams that require a net data structure different
from the device profile.
Bit 6 = 0: Normal data exchange.
•
Bit 6 = 1: Testing the bus connection: The inverter returns the telegram un-
changed to the master.
Bit 5 = 0: Normal data exchange.
•
(Bit 5 = 1: Not supported in the inverter.)
Bits 0 ... 4: Address of the inverter.
•
See Section User data range of the USS telegram (Page 221).
Checksum (exclusive or) across all telegram bytes – with the exception of
BCC.
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A