LG Electronics 120S user manual Function code types and memory mapping, Modbus addressing rules

Chapter 8 Communication Functions

7) Function code types and memory mapping

Code	Function code name	Modicon PLC	Remark
		Data address
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."

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