HP-71b CMT-64E Eprom - Whats under the black goop ?

[J-F Garnier]

(03-14-2020 07:00 AM)coitboy2000 Wrote:  I was wondering what lies beneath the black dob of goop ? I guess an integrated circuit to account for the lack of 32 pins (13 only on module, 32 on PLCC32 eprom) ?

There is a HP specific integrated circuit that makes the interface between the standard 8-bit wide EPROM and the 4-bit HP71 bus. The circuit reference is 1LJ4, it is also used in packaged form in the card reader memory modules both from CMT and HHP.

A few years ago, Paul Berger and I attempted to document it and identify the pinout, see this document:
http://www.jeffcalc.hp41.eu/misc/files/hhp.pdf

I know that one member of this forum once (long ago) said he has the datasheet of the 1LJ4 circuit, but I never succeeded to get it, unfortunately.

J-F