User Data Range Of The Uss Telegram - Siemens SINAMICS G120 CU230P-2 HVAC Operating Instructions Manual

Configuring the fieldbus
6.2 Communication via RS485
ADR
The ADR range contains the address of the slave node (e.g. of the inverter). The individual
bits in the address byte are addressed as follows:
Special
telegram
● Bit 5 broadcast bit
● Bit 6 mirror telegram
● Bit 7 special telegram
BCC
BCC (Block Check Character). It is an exclusive OR checksum (XOR) over all telegram
bytes with the exception of the BCC itself.
6.2.2.4

User data range of the USS telegram

The user data range of the USS protocol is used to transmit application data. This comprises
the parameter channel data and the process data (PZD).
The user data occupy the bytes within the USS frame (STX, LGE, ADR, BCC). The size of
the user data can be configured using parameters p2023 and p2022. The structure and
sequence of the parameter channel and process data (PZD) are shown in the figure below.
Figure 6-6
122
7
6 5
Mirror Broadcast
bit
telegram
Bit 5 = 0: normal data exchange. Bit 5 = 1: Address (bits 0 ... 4) is not evaluated (is not
supported in SINAMICS G120!).
Bit 6 = 0: normal data exchange. Bit 6 = 1: The slave returns the telegram unchanged to
the master. Is used to test the bus connection.
Bit 7 = 0: normal data exchange. Bit 7 =1 to transfer telegrams that require a net data
structure different from the device profile.
USS user data structure
Frequency inverters with Control Units CU230P-2 HVAC, CU230P-2 DP, CU230P-2 CAN
4 3 2
5 Address bits
Operating Instructions, 01/2011, FW 4.4, A5E02430659B AD
1
0