FATEK M Series User Manual page 23

The corresponding IR or OR number calculation of the NI/O module starts from the first expansion
module. The first NI channel corresponds to the first IR register (R34768). Adding R34768 with the number
of IR used by the first NI channel gives the IR number of the second NI channel. Adding the IR number of
the second NI channel with the number of IR used by the second NI channel gives the IR number of the
third NI channel. All other numbers can be obtained accordingly. Similarly, the first NO channel corresponds
to the first OR (R35024). Adding R35024 with the number of OR used by the first NO channel gives the OR
number of the second NO channel. (In the cumulative calculation of NI channels, care only for NI channels
and disregard DI/O and NI. Similarly, in the case of NO channels, disregard DI/O and NI channels.) The
following figure helps users find out the relation between NI/O channels and PLC's IR and OR.
The M-series PLC will automatically detect the expansion module when it is turned on, and then
automatically set the IR and OR, the user does not need to make any settings.
Analog expansion module IR, OR number
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Chapter 2 Expansion of M-Series PLC
M-Series PLC Expansion Module User Manual