9
DEVICE EXPLANATION
9.3  Internal System Devices
9.3.1  Function devices (FX, FY, FD)
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Device Explanation
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CPU Module Processing 
Time
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Procedure for Writing 
Program to CPU Module
AppendicesIndex
9.3  Internal System Devices
Internal system devices are used for system operations.  
The allocations and sizes of internal system devices are fixed, and cannot be changed by 
the user.
9.3.1  Function devices (FX, FY, FD)
(1) Definition
Function devices are used in subroutine programs with arguments.
The function devices write/read data between a subroutine call source with argument 
and a subroutine program with argument.
(2) Applications of function devices
Because the function devices used for each subroutine program CALL source can be 
set, the same subroutine program can be used without regard to other subroutine 
CALL sources.
(3) Types of function devices
There are 3 function device types: function input devices (FX), function output devices 
(FY), and function register devices (FD).
(a) Function input devices (FX)
 • These devices are used to designate inputs of ON/OFF data to a subroutine 
program.
 • In the subroutine program, these devices are used for reading and 
processing bit data designated by subroutine with argument CALL 
instruction.
 • All the CPU module bit data designation devices can be used.
(b) Function output devices (FY)
 • These devices are used to designate outputs of subroutine program operation 
results (ON/OFF data) to the subroutine program CALL source.
 • The operation results are stored at the device designated by using subroutine 
programs with arguments.
 • All bit data designation devices except CPU module inputs (X, DX) can be used.
Diagram 9.42 Application example of function devices
M0 D0P0 X0
CALL
FD1 R0
FY1
MOV
SET
RET
X0 FX0
P0
If FX0 and FD1 are used at the subroutine program, and if M0 and D0 are designated by the 
subroutine CALL instruction, the M0 ON/OFF data is transferred to FX0, and the D0 data is 
transferred to FD1.
[Subroutine program CALL source]
[Subroutine program]
Example