Anyone knows what is port 1FH

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Postby chernandezba » Fri, 23.02.2018 22:23:37


I'm seeing some demos and games which read port 1F. For example "Uwol - Quest for Money" (and all conversions from mojon twins), xonix, alteregobeta, and some others.
If I return the usual value FF on my ZEsarUX emulator (or floating ula value), these games seem to read some key? xonix for example, the sprite is always moving to the right. on uwol, seems to read a key so the menus doesn't wait a keypress...
If I return a 0 value for this port, these games work... :)

So, I have found references to port 1F for betadisk ports and also "power of sound turbo-AY (bit 0 of port #1F)". But doesn't seem to be related with keyboard...

Anyone knows why these demos are reading port 1F?

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Postby VBI » Sat, 24.02.2018 10:48:41

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Postby DDp » Sat, 24.02.2018 11:34:17

Also, ... id=1000220 .
For schematic Issue4(1989) port decoding with A7=0,A6=0,A5=0,RD=0,IORQ=0,M1=1.
D7..D5 always read as 0.
D356 47C0 35F8 F55E 8A52 A88F F3F8 B003 03EB 3D7F
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Postby chernandezba » Sat, 24.02.2018 13:18:15

OMG! My memory is not good! :( Kempston joystick...
So, these games doesn't work well if kempston joystick not found (and 255 value is returned)

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