Mitsubishi MELSEC Q Series Programming Manual page 496

ECALL(P)
(5) From
(6) The device used in the argument of the ECALL instruction should not be used in a
subroutine program.
If used, it will not be possible to obtain accurate calculations. (Refer to the following
program example.)
Incorrect operation example
The following example shows the operation performed when D0 is specified for FD0 in the
subroutine program and D1 is used in the subroutine program.
[Program example]
[Operation performed after subroutine program execution]
Before the execution
of subroutine program
D0
D1
D2
D3
FD0
*1: Stores the execution result of the subroutine program.
*2: Replaced by the value of the function device.
*3: D1 does not reflect the value of the function device.
7-122
to can be used by the ECALL instruction.
S1 S5
Immediately after the
execution of ECALL
instruction
0 D0
10 D1
100 D2
Transfer
1000 D3
Indefinite
Indefinite
FD0
Indefinite
Indefinite
At the time of
subroutine program
execution
0 D0 0
10 D1 110 *1
100 D2 100
1000
D3 1000
0
33 *1
10 1 *1
FD0
100 100
1000 1000
After the execution
of RET instruction
D0 33 *2
D1 110 *3
D2 100 *2
Transfer
D3 1000 *2
Indefinite
Indefinite
FD0
Indefinite
Indefinite