System variable $A_PBB_IN [n] used to read and write a data byte (8 bits) from the PLC I/O.
The dimension is configured via $MN_PLCIO_NUM_BYTES_IN.(MD10394)
Start addr. of the directly readable input bytes of the PLC I/Os $MN_PLCIO_LOGIC_ADDRESS_IN (MD10395)

The machine data MD10394 $MN_PLCIO_NUM_BYTES_IN and MD10395
$MN_PLCIO_LOGIC_ADDRESS_IN must be consistent with the PLC-side configuration

Examble I100.0

$MN_PLCIO_NUM_BYTES_IN = 1
$MN_PLCIO_LOGIC_ADDRESS_IN 100

NC Program
DEFBOOL I100_0 ; I100.0

I100_0 = ($A_PBB_in[0] B_AND 1)