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30 Applied Instructions (External Device Communication)

FXCPU Structured Programming Manual

[Basic & Applied Instruction]

Appl
ied

 In

stru
cti

ons 

(R

eal
 T

im

e 

C

lock
 Contr

ol)

Ap

plied
 Instru
ctio
ns 

(E

xt

er

na

l De
vi

ce

)

App
lied Instr

ucti

ons 

(Ex
tensi
on 

Functi

on)

Ap

pl

ied In
struct

ions 

(O

thers)

Appl
ied

 Instru
cti

ons
 

(B

lock
 Dat
a 

O

per

at

io

n)

App
lie

d Instr

uction
s 

(Charac

ter 

Stri

ng C

ontrol

)

Ap

pl

ied Inst

ruct
io

ns 

(D

ata

 Op
eration 3

)

Appl
ied

 In

stru
cti

ons 

(D

ata C
om

par

ison

)

App
lie

d Instr

uction
s 

(D

ata
 T

abl

e 

O

peration

)

Appli
ed In
struc
tions

(E

xt

ernal Devi

ce 

Comm

uni

cat

ion)

1) The instruction is provided in the FX

3U

 and FX

3UC

 PLCs Ver. 2.40 or later.

The instruction is provided in the FX

3G

 PLC Ver. 1.30 or later.

2) It is not permitted to use an "ADPRW" instruction and a following instruction for the same port:

- "RS or RS2" instruction

- "IVCK, IVDR, IVRD, IVWR, IVBWR

*1

, IVMC" instruction

- "FLCRT

*1

, FLDEL

*1

, FLWR

*1

, FLRD

*1

, FLCMD

*1 

or FLSTRD

*1

" instruction

3) Some restrictions to applicable devices

S1: Excluding special auxiliary relays (M) and Special data register (D).
S2: The FX

3U

 and FX

3UC

 PLCs only are applicable.

*1.

The instruction is not provided in the FX

3S

, FX

3G

 and FX

3GC

 PLCs.

The following table shows the required command parameters for each command code.

1H
Read Coils

MODBUS Address:
0000H to FFFFH

Device Count: 1 to 2000

PLC Destination Device (head address)
Applicable Devices D, R, M, Y, S

Block Length

(

+15) 

÷16

*2

2H
Read Discrete
Inputs

MODBUS Address:
0000H to FFFFH

Device Count: 1 to 2000

PLC Destination Device (head address)
Applicable Devices D, R, M, Y, S

Block Length

(

+15) 

÷16

*2

3H
Read Holding
Register

MODBUS Address:
0000H to FFFFH

Device Count: 1 to 125

PLC Destination Device (head address)
Applicable Devices D, R

Block Length

4H
Read Input 
Register

MODBUS Address:
0000H to FFFFH

Device Count: 1 to 125

PLC Destination Device (head address)
Applicable Devices D, R

Block Length

5H
Write Single Coil

MODBUS Address:
0000H to FFFFH

0 (fixed)

PLC Sourse Device (head address)

Applicable Devices

D, R, K, H, X, Y, M, S
(D, R, X, Y, M, S can be
indexed.)

Block Length

1 Point

6H
Write Single
Register

MODBUS Address:
0000H to FFFFH

0 (fixed)

PLC Source Device (head address)

Applicable Devices

D, R, K, H
(D, R can be indexed.)

Block Length

1 Point

7H
Read Exception
State (Available only in
FX

3U

 and FX

3UC

 PLCs)

0 (fixed)

0 (fixed)

PLC Destination Device (head address)
Applicable Devices D, R

Block Length

1 Point

8H
Diagnosis
(Available only in FX

3U

and FX

3UC

 PLCs)

Sub-function: 0H
Loop-back Test

Sub-function Data
(loop-back data): 0 to 65535

Loop-back Test Data
(Slave response: echo of 

)

Applicable Devices D, R
Block Length

1 Point

Sub-function: 1H
Restart
Communication

Sub-function Data:
0x0000: Do Not Reset
Event Log
0xFF00: Reset Event Log

(Slave response: echo of 

)

Applicable Devices D, R

Block Length

1 Point

Sub-function: 2H
Return
Diagnostic Register

0 (fixed)

PLC Destination Device (head address)
Applicable Devices D, R
Block Length

1 Point

*2.

This calculation formula is applicable when the applicable device is D or R.