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Anyone knows what is port 1FH

PostPosted: Fri, 23.02.2018 22:23:37
by chernandezba
Hi

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?


Thanks

Re: Anyone knows what is port 1FH

PostPosted: Sat, 24.02.2018 10:48:41
by VBI
Image

Re: Anyone knows what is port 1FH

PostPosted: Sat, 24.02.2018 11:34:17
by DDp
Also, http://www.worldofspectrum.org/infoseek ... 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.

Re: Anyone knows what is port 1FH

PostPosted: Sat, 24.02.2018 13:18:15
by chernandezba
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)

Thanks!