Communication Procedure - Siemens SINAMICS G120 CU240B-2 Operating Instructions Manual

Connection to a fieldbus
6.4 Communication via RS485
Table 6- 33
Example
11 h
06 h
00 h
63 h
55 h
66 h
xx h
xx h
The response returns the register address (bytes 2 and 3) and the value (bytes 4 and 5) that
was written to the register.
Table 6- 34
Example
11 h
06 h
00 h
63 h
55 h
66 h
xx h
xx h
6.4.3.5

Communication procedure

Procedure for communication in a normal case
Normally, the master sends a telegram to a slave (address range 1 ... 247). The slave sends
a response telegram to the master. This response telegram mirrors the function code, and
the slave enters its own address in the telegram, which enables the master to assign the
slave.
The slave only processes orders and telegrams which are directly addressed to it.
Communication errors
If the slave detects a communication error on receipt (parity, CRC), it does not send a
response to the master (this can lead to "setpoint timeout").
152
Structure of a write request for slave number 17
Byte Description
0 Slave address
1 Function code
2 Register start address "High" (write register 40100)
3 Register start address "Low"
4 Register data "High"
5 Register data "Low"
6 CRC "Low"
7 CRC "High"
Slave response to the write request
Byte Description
0 Slave address
1 Function code
2 Register start address "High"
3 Register start address "Low"
4 Register data "High"
5 Register data "Low"
6 CRC "Low"
7 CRC "High"
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA