MANUEL STA46 Modbus TCP
JP Viskovic 30/08/2005 OEE-F 8
1-4-2 I/O memory area (DM) Read Multiple Registers
[Function]
Reads registers in I/O memory area
[Request]
Length Data
Function Code 1 Byte
0x03
Starting Address 2 Bytes 0x0000-0x7FFF(*)
Quantity of Registers 2 Bytes 1-125(0x7D)
(*)Useful range of Start Address depends on allocated area.
[Response]
Length Data
Function Code 1 Byte
0x03
Byte Count 1 Byte N x 2(*)
Register Value N x 2 Bytes
(*)N=Quantity of Registers
Example: read 3 words (DM 1000 to DM 1002)
Request Response
Data
Data
Function Code 0x03 Function Code 0x03
Starting Address(H) 0x03 Byte Count 0x06
Starting Address(L) 0xE8 Register Value(H)DM1000 0xAB
Quantity of Registers(H) 0x00 Register Value(L) DM1000 0x12
Quantity of Registers(L) 0x03 Register Value(H)DM1001 0x56
Register Value(L) DM1001 0x78
Register Value(H)DM1002 0x97
Register Value(L) DM1002 0x13
DM 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1000
A B 1 2
1001 5 6 7 8
1002 9 7 1 3
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