Need datasheet for INS8154

Hi all,

I'm renovating an old ACORN System 1 computer (circa 1979) and need a datasheet for an old and obsolete part - INS 8154. It's a 40 pin IC, with I/O ports and a small amount of RAM.

I've tried the web search engines and been in contact with National (the original manafacturer) but not had any luck.

Can anybody please help.

Thanks, Joe