Communication via RS485
5.4 Communication using Modbus RTU
Fieldbuses
142 Function Manual, 04/2018, FW V4.7 SP10, A5E34229197B AE
Table 5- 27 Response for unsuccessful read operation - read request still not completed
20 h
0001 h
2F00 h
0004 h
2
3,4
5,6
7,8
Number of following data bytes (20 h: 32 bytes
16 registers)
40601: Check value 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
xx h
9
CRC "Low"
Write parameter
Example: Set p1121 = 12.15
Table 5- 28 Write parameter request: Writing the parameter value of p1121 from slave number 17
10 h
0258 h
000A h
14 h
0001 h
2F10 h
8002 h
0101 h
1001 h
0461 h
0000 h
0801 h
4142 h
1
2,3
4,5
6
7,8
9,10
11,12
13,14
15,16
17,18
19,20
21,22
23,24
Function code (write multiple)
Register start address
Number of registers to be written to (40601 … 40610)
Number of data bytes (10 registers, each 2 bytes = 20 bytes)
40601: C1 (activate request)
40602: Function 2F h (47), request length 16 bytes (10 h)
40603: Request reference = 80 h, request identifier = 2 h (write)
40604: DO-Id = 1, number of parameters = 1
40605: Attribute, number of elements = 1
40606: Parameter number = 1121
40607: Subindex = 0
40608: Format + number of values
40609: Parameter value 12,15
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