"I did a project with an NEC 75P008 4-bit micro..."
...it has no conditional jump instructions - only conditional skip instructions."

Yep, I did an NEC 7554 project once. I'd like to say that I remember it well, but it was many years ago, so I don't really remember it all that well. However, what I do remember was all the skip stuff and, at the time, figured that I would not likely run across that branching model again. That was until I met up with the Microchip PICs...