Chapter 8 Communication Functions
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7) Function code types and memory mapping
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
• MASTER-K120S 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
MASTER-K120S main unit starts its address from 0 and matches with 1 of Modicon products' data address. So MASTER-
K120S's 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 MASTER-K120S.
9) The size of using data
As for data size, MASTER-K120S main unit supports 128 bytes in ASCII mode and 256 bytes in RTU mode. The maximum
size of the Modicon products is different from each other kind. So refer to "Modicon Modbus Protocol Reference Guide."