Chapter 8. Communication Function
8-64
7)
Function code types and memory mapping
Code Function code name
Modicon PLC
Data address
GLOFA-mapping Remark
01 Read Coil Status 0XXXX(bit-output) %MX0~%MX9999
Read bits
02 Read Input Status 1XXXX(bit-input) %MX0~%MX9999
Read bits
03 Read Holding Registers 4XXXX(
word-output
) %MW0~%MW9999
Read words
04 Read Input Registers 3XXXX(
word-input
) %MW0~%MW9999
Read words
05 Force Single Coil 0XXXX(bit-output) %MX0~%MX9999
Write bit
06 Preset Single Register 4XXXX(
word-output
) %MW0~%MW9999
Write word
15 Force Multiple Coils 0XXXX(bit-output) %MX0~%MX9999
Write bits
16 Preset Multiple Registers 4XXXX(
word-output
) %MW0~%MW9999
Write words
8) Modbus addressing rules
GM7U main unit starts its address from 0 and matches with 1 of Modicon products' data address. So GM7U's
address, n matches n+1 of Modicon products' address. Also, GM7U main unit has continuous M area without
any division of output contact points (0XXXX), input contact points (1XXXX), output registers (4XXXX), input
registers (3XXXX). 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 GM7U.
Output contact points
(0XXXX), In
put contact points
(1XXXX),
Output registers
(4XXXX), In
put registers
(3XXXX)
9)
The size of the data in use
As for data size, GM7U 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."
1) GM7U main unit doesn't have any division between input and output area like Modicon PLC, when it
supports Modbus protocol communication. It uses only M area. So the user must be caution to in set input
and output area in M area for Modbus protocol communication.
REMARK
Highest data of data address dividing output contact point, input contact point,
output register, and input contact register in Modicon products.
To Next Page
Loading...
