Siemens SINAMICS G120P, Operating Instructions Manual

Page: 220 / 496

Operation
6.8 Communication via RS485
Inverter cabinet units
220
Operating Instructions, 12/2014, A5E32923362A
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 Structure of a USS telegram
Telegram part Description
Start delay / re-
sponse delay
There is always a start and/or response delay between two telegrams (see
alsoTime-out and other errors (Page 227)).
STX An ASCII character (02 hex) indicates the beginning of the message.
LGE The telegram length "LGE" is calculated as follows:
LGE = user data (n bytes) + ADR (1 byte) + BCC (1 byte)
ADR
• 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.
Net data See Section User data range of the USS telegram (Page 221).
BCC Checksum (exclusive or) across all telegram bytes – with the exception of
BCC.