Mitsubishi 00JCPU User Manual page 421

In subroutine programs with argument passing, do not use any devices that are used by the function register.
If this occurs, function register values will not be normally passed to the calling program.
Figure 9.50 Ladder example in which use of devices is not allowed in a subroutine program with argument passing
Remark
For use of function devices, refer to the following.
MELSEC-Q/L Programming Manual (Common Instruction)
CALLP P0 D0
P0
CHAPTER9 DEVICES
*
D R0 R10 FD0
MOV K0 D3
Since D0 to D3 are used for FD0,
D3 cannot be used in the
subroutine program.
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