How does it force $de? In c128 mode $fffa seems to contain $ff05, so it would become $ffde? I had assumed it was looking for the keyboard scan, but I can't figure out why they would do it like that. On 02/10/2022 18:57, groepaz_at_gmx.net wrote: > Its really kindof weird. The cartridge has a circuit to listen to the > address > bus. The button "arms" the circuit and issues a NMI, and when there is $fffa > it forces $de on the databus. Now a side effect of how the keyboard scanner > works is that you get a 60Hz pulse on some pin(s) on the joystick port. This > pulse is now used to "disarm" the NMI logic.Received on 2022-10-02 23:00:04
Archive generated by hypermail 2.3.0.