Internal System Devices; Function Devices (Fx, Fy, Fd) - Mitsubishi Electric MELSEC-Q Series User Manual

10 DEVICES

10.3 Internal System Devices

10.3.1 Function devices (FX, FY, FD)

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Internal system devices are devices used for system operations.
The allocations and sizes of internal system devices are fixed, and cannot be changed
by the user.
(1) Definition
(a) Function devices are devices used in sub-routine program with arguments
to permit data transfers between the sub-routine program with argument,
and the CALL source for that sub-routine.
Example
If FX0 and FD1 are used at the sub-routine program, and if M0 and D0 are designated by the sub-routine
CALL instruction, the M0 ON/OFF data is transferred to FX0, and the D0 data is transferred to FD1.
[Sub-routine program CALL source]
X0
CALL
(b) Because the function devices used for each sub-routine program CALL
source can be set, the same sub-routine program can be used without
regard to other sub-routine CALL sources.
(2) 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 sub-
routine program.
• In the sub-routine program, these devices are used for reading and
processing bit data designated by sub-routine with argument CALL
instruction.
• All the Basic model QCPU bit data designation devices can be used.
(b) Function output devices (FY)
• These devices are used to designate outputs of sub-routine program
operation results (ON/OFF data) to the sub-routine program CALL source.
• At sub-routine program with arguments, the operation results are stored at
the designated device.
• All bit data designation devices except Basic model QCPU inputs (X, DX)
can be used.
[Sub-routine program]
P0
P0 M0 D0
MELSEC-Q
FX0
MOV FD1 R0
RET
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