That is very likely what I was remembering. As I said, this was long ago (as in 30+ years ago) so I very well may have been remembering this multi-level ROM se

That is very likely what I was remembering. As I said, this was long ago (as in 30+ years ago) so I very well may have been remembering this multi-level ROM setup and mixing it up with three valued logic. I do concur that this would be an interesting topic for another post.