Operating Instructions

Communication via RS485
5.4 Communication using Modbus RTU
Fieldbuses
Function Manual, 04/2018, FW V4.7 SP10, A5E34229197B AE
143
Table 5- 29 Start parameter request: Writing the parameter value of p1121 from slave number 17
Value
Byte
Description
11 h
0
Slave address
06 h
0258 h
0007 h
0010 h
1
2,3
4,5
6,7
Function code (write)
Register start address
Number of registers to be written to (40601 … 40610)
Number of registers
xx h
xx h
8
9
CRC "Low"
CRC "High"
Table 5- 30 Response for successful write operation
Value
Byte
Description
11 h
0
Slave address
06 h
20 h
0002 h
2F04 h
8002 h
0101 h
1
2
3,4
5,6
7,8
9,10
Function code (write)
Number of following data bytes (20 h: 32 bytes
≙
16 registers)
40601: DS47 Control = 2 (request was executed)
40602: Function code 2F h (47), response length 4 bytes
40603: Request reference mirrored = 80 h,
response identifier = 2 (change parameter)
40604: DO-ID = 1, number of parameters = 1
xx h
xx h
11
12
CRC "Low"
CRC "High"
Table 5- 31 Response for unsuccessful write operation - write request still not completed
Value
Byte
Description
11 h
0
Slave address
06 h
20 h
0001 h
2F00 h
0004 h
1
2
3,4
5,6
7,8
Function code (write)
Number of following data bytes (20 h: 32 bytes
≙
16 registers)
40601: DS47 Control = 1 (request is processed)
40602: Function 2F h(47), response length 0 (fault)
40603: Error code: 0004 Response Not Ready (response has still not been
issued)
xx h
xx h
9
10
CRC "Low"
CRC "High"