Usually you can only connect 1 EXP4040 to an M-series PLCs and MD-HMI since the limit of total number of I/O is 96 inputs and 96 outputs . But for extreme situation that call for more than 96 inputs and 96 outputs there is a way to force the PLC to accept up to 128 inputs and 128 outputs (maximum) but only for some newest CPU firmware version (r47 and above). Please contact us via email if you need more information since this is an undocumented feature.
