Internal System Devices; Function Devices (Fx, Fy, Fd) - Mitsubishi Electric Q01UCPU User Manual

4.3

Internal System Devices

Internal system devices are provided for system operations.
The allocations and sizes of internal system devices are fixed, and cannot be changed by the user.
4.3.1

Function devices (FX, FY, FD)

Function devices are used in subroutine programs with argument passing.
Data are read or written between such subroutine programs and calling programs, using function devices.
When FX0, FY1, and FD2 are used in a subroutine program, and if X0, M0, and D0 are specified with a
Ex.
subroutine program call instruction, on/off data of X0 and FY1 are passed to FX0 and M0 respectively,
and D0 data are passed to FD2.
[Calling program]
X0
(1) Applications of function devices
Because a device in each calling program can be determined by using a function device for subroutine programs,
the same subroutine program can be used without considering other calling programs.
(2) Types of function devices
The following three types of function devices are available.
• Function input (FX)
• Function output (FY)
• Function register (FD)
(a) Function input (FX)
• The function input is used to pass on/off data to a subroutine program.
• Bit data specified by a subroutine call instruction with argument passing are fetched into a subroutine
program and they are used for operations.
• All bit devices for the CPU module can be used.
(b) Function output (FY)
• The function output is used for passing an operation result (on/off data) in a subroutine program to a
calling program.
• An operation result is stored in the device specified in the subroutine program with argument passing.
• All bit devices except for input devices of the CPU module (X and DX) can be used.
P0
CALL P0 X0 M0 D0
[Subroutine program]
FX0
MOV FD2
SET
FY1
CHAPTER 4 DEVICES
R0
RET
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