Mitsubishi MELSEC-A Series Reference Manual page 220

7. DATA LINK SETTINGS
(2)
(3)
(4)
As for I/O assignment of remote I/O station, a slot in which a module is installed
cannot be assigned as an empty slot (S1: 0 point, S2: 16 points, S3: 32 points, S4: 48
points, S5: 64 points). If assigned to an empty slot, a "UNIT VERIFY ERROR" will
occur.
If slot 0 in a remote I/O station is empty, at least 16 points (S2, S3, S4, S5) must be
assigned to an empty slot.
If S1 is set for an empty slot, a "UNIT VERIFY ERROR" will occur.
When assigning inputs and outputs to a special function module, set the number of
points of the module actually installed. If the wrong number of points is set, and the
RFRP or RTOP instruction is executed, an error will occur.
POINT
I/O assignment cannot be used to change the number of I/O points for an input/
output module connected to the A0J2P25(S3)/R25 (compact type remote I/O
station module).
Assign the same number of I/O points that is assigned to a remote I/O station
configured with the A0J2P25(S3)/R25.
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