User guide
30 MDX-ETHERNET User Guide
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7.7 How to read and write cyclic Modbus
MDX-ETHERNET supported various Modbus function codes to write and read cyclic.
The modbus address for IN and OUT cyclic is dependent of the function use see table
7.7 for more information.
Table 7.7 Cyclic Modbus address for IN and OUT
Example with function code FC16: if drive mode is in default parameter
(Pr 15.34 = disabled, Pr 15.20 = 642 and Pr 15.21 = 121) Modbus address 0 allow to
write to Pr 6.42 and address 2 to Pr 1.21.
Drive mode is in default
parameter
Pr 15.09 = 2 registers
or
Pr 15.09 = 1 register
First address for cyclic
IN data
(Pr 15.10 to Pr 15.19)
Master PLC drive
First address for cyclic
OUT data
(Pr 15.20 to Pr 15.29)
Master PLC drive
Register Type
and
address range
FC1
Read Coils
Modbus address = 000
Coils (0x)
000-FFF cyclic area
FC2
Read Discrete Inputs
Modbus address = 000
Discrete Inputs (1x)
000-FFF cyclic area
FC3
Read holding Registers
Modbus address = 256 Modbus address = 000
Holding Registers (4x)
000 -1FF cyclic area
210 -FFFF non-cyclic
area
FC4
Read Input Registers
Modbus address = 000
Input Registers (3x)
000-FFF cyclic area
FC5
Write Single Coil
Modbus address = 000
Coils (0x)
000-FFF cyclic area
FC6
Write Single Register
Modbus address = 256 Modbus address = 000
Holding Registers (4x)
000 -1FF cyclic area
210 -FFFF non-cyclic
area
FC15
Write Multiple Coils
Modbus address = 000
Coils (0x)
000-FFF cyclic area
FC16
Write Multiple Registers
Modbus address = 256 Modbus address = 000
Holding Registers (4x)
000 -1FF cyclic area
210 -FFFF non-cyclic
area
FC23
Read/Write Multiple
Registers
Modbus address = 256 Modbus address = 000
Holding Registers (4x)
000 -1FF cyclic area
210 -FFFF Non-cyclic
area
- Parameter Pr 15.34 (Compression of cyclical data) define if each parameter take 1 or
2 words in only cyclic data.
- Parameter Pr 15.09 (Modbus register number by acyclic parameter) define if each
parameter take 1 or 2 words in only non-cyclic data.
With Master PLC, LEROY-SOMER advise to used Function 03 to read and Function 16
to write (this functions is generally used in all PLC).
NOTE
NOTE