Am Mittwoch, 5. Oktober 2022, 22:40:03 CEST schrieb Jim Brain: > According to the schematics in the download: > > * The switch sets a 7474 flip flop (which means the bouncing of the > switch would not affect anything) > * The output is then fed into a second flop > * The second flop is clocked by the joystick port > * once clocked, the NMI line is pulled low *AND* the $de on the data > bus is armed to be injected when A15-A0 = 1111111111111X1X > * The entire thing can be turned off with a poke to $de00-de7f of x1xxxxxx > > So, it looks to me that the joyport connection is required for the NMI > to be asserted. AH! My TTL foo is too rusty, dont remember any of the flipflop properties (or even schematic symbols =P). So it is indeed waiting for "not in system NMI". Seems odd - i wonder what kind of scenario they had in mind that would be solved by this. -- http://hitmen.eu http://ar.pokefinder.org http://vice-emu.sourceforge.net http://magicdisk.untergrund.net Fortschritt ist wie eine Horde Schweine. Beides hat viel Gutes, aber man darf sich nicht wundern, dass alles voller Scheisse ist.Received on 2022-10-06 00:00:05
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