Phoenix Contact SCK-C-MODBUS User Manual page 34

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34
PHOENIX CONTACT
You must design the Modbus data request for the communication module according to the
following schematic:
Client Function
address code
03 03
Client No. Read holding
3 register
Response: 03 03 xx xx xx xx xx ... (address + function code + data + CRC)
Example data record:
Request for module information data from module No. 3:
Tx: 03 03 04 B1 00 15 D4 F0
Response from module:
Rx: 03 03 2A 00 01 01 23 45 67 89 AB CD EF 43 53 2D 4B 2D 43 4F 4D 42 44 53 55 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 97 3A
Response in plain text:
03  Addressed module ID
03  Function code
2A  Number of subsequent bytes (here: 42 bytes, 21 registers)
00 01  Module ID (SCK-C-MODBUS module type)
01 23 45 67 89 AB CD EF  4 registers, module serial number
43 53 2D 4B 2D 43 4F 4D 42 44 53 55 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00  Module designation in ASCII code: "SCK-C-MODBUS" (occupies a maximum
of 32 characters)
97 3A  Checksum
Start Total number of
register registers
04B1 0015
1201 21
CRC
(Cyclic Redundancy
Check)
D4F0
Resulting
checksum
105608_en_00