I’m not sure why this datasheet is in my collection, but I assume it’s because I stumbled across this drive in something, so since I took the trouble in 2015 to find and download it, I’ve added it here. If I eventually find out “why” I had it, I’ll update this entry.

This is a help card for a DAP4 with an 1526-nn CPU installed for connection to an 8890 mainframe.

The 8251 is a Programmable Communication Interface controller and is found inside a DAP4 CPU board 1528-xx and form the interface between the CPU board electronics and the external personality interface board.