The machine had 0402-03 when it was built. I have upgraded the firmware for DNC and it is now 0402-05. The ladder copy I have is for the PMC-L on the main board. Its in the factory operator manual for this mill.
I removed the LSI chip and nothing appeared to change. Still have the 446 alarm. Diagnostic parameter 28.0 and 28.1 are both 0 which indicates it is seeing the Additional I/O card. I also proved the ladder has 4th axis code as I can toggle the 4th axis interlock G128.3 by changing state of the table unclamp input.
Yes it would appear so. Replaced the card and the 446 alarm is gone. Not sure what to do with the faulty card, no idea how much it would cost to repair and keep as a spare.