I thought the Jupiter Ace was pretty straightforward,
to be honest.
The ACE used that obnoxious trick of contenting a totem pole output in
series with a 1k resuistor against a 3-state output. If the latter was
enabled, it drove the output signal (overriding the signal for m the 1k
resistor), if the latter was disabled, then a totem pole drive the output.
That 'trick' is not going to be mentioned in any introductory book on
digital electroncs (thank %deity!), so it might well cause a lot of
confusion.
-tony