Mitsubishi Electric MELSEC-Q00U(J)CPU User Manual page 64

(c) Start XY setting
When the start XY has not been entered, the CPU module automatically assigns it. For this reason, the start
XY setting of each slot may be duplicated with the one assigned by the CPU module in the case of 1) or 2)
below.
1.
Start XY values are not in the correct order.
2.
Slots with and without the start XY setting (automatically assigned slot) are mixed
The following figure shows an example of start XY duplication.
Do not set duplicated start XY for each slot.
Specify start XY in the additional module to prevent the duplication of start XY.
Input "0060" to "start XY" in slot2.
Ex.
Duplication of start XY will result in "SP. UNIT LAY ERR." (An error occurs even the module is not mounted.)
62
Automatically assigned slot
0 1 2 Slot number
Number of I/O points
32 points 32 points 32 points
X40 X20 X40
to to to I/O number
X5F X3F X5F
Start XYs are overlapped