Originally Posted by Golden Child
Original Grappler schematic:

https://archive.org/details/manualsonline-id-6b56a0aa-4089-4658-a2c6-de559ed3a773/page/n17/mode/2up

Interesting, this one doesn’t automatically generate strobe pulses, doesn’t use Apple’s trick of flipping a ROM address line while waiting for the printer to acknowledge a character, doesn’t generate interrupts, and doesn’t have DIP switches. Looks like a very simple card.

Originally Posted by Golden Child
The ProGrappler manual doesn't have schematics unfortunately.

https://archive.org/details/ProGrappler/mode/2up

I was doing a little bit of circuit tracing on the ProGrappler and two of the data lines are swapped I think. I'll have to check because I can't remember exactly.

According to my notes:

"I was looking at the prograppler dump and it looked really horrible, so I thought I'd do some checking on the board with a multimeter,
looks like they did a little bit of "protection" where they swapped d3/d4 and a2/a3 and a6/a7."

Yeah, looks like by this time they were trying to make it harder for people to clone the card. This one probably requires more reverse-engineering to emulate.