Chapter 8 Modbus Communication
8-3
7) Function code type
Code Function Code Name
Modicon PLC
Data Address
Remark
01 Read Coil Status
0XXXX(bit-
output)
Read bits
02 Read Input Status 1XXXX(bit-input) Read bits
03 Read Holding Registers
4XXXX(word-
output)
Read
words
04 Read Input Registers
3XXXX(word-
input)
Read
words
05 Force Single Coil
0XXXX(bit-
output)
Write bit
06 Preset Single Register
4XXXX(word-
output)
Write word
15 Force Multiple Coils
0XXXX(bit-
output)
Write bits
16 Preset Multiple Registers
4XXXX(word-
output)
Write
words
◈ PLC Option Card Mapping
Bit area Word area
Address Data area Address Data area
h0000 P area h0000 P area
h1000 M area h1000 M area
h2000 L area h2000 L area
h3000 K area h3000 K area
h4000 F area h4000 F area
h5000 T area h5000
T area
(current value area)
h6000 C area h6000
C area
(current value area)
- - h7000 S area
- - h8000 D area
8) Modbus addressing rules
PLC option card starts its address from 0 and matches with 1 of Modicon products' data address. So
PLC option card address n matches n+1 of Modicon products' address. This means that the output
contact point 1 (0001) of Modicon products is marked as communication address 0 and the input
contact point 1 (0001) of Modicon products is marked as communication address 0 in PLC option card.
9) The size of using data
As for data size, PLC option card supports 128 bytes in ASCII mode and 256 bytes in RTU mode. The
maximum size of the Modicon products is different from each other’s kind. So refer to "Modicon
Modbus Protocol Reference Guide."
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