ZX80 joystick port

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gertk
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Joined: Sun Oct 14, 2012 9:09 pm

ZX80 joystick port

Post by gertk »

Hi,

I have added a ZX80 emulation mode to my NXP81 project and found some 'flicker free' games like Pacman and Krazy Kong which seem to work quite nice. On the opening screen you can select two kind of joystick modes: Sinclair and Kempston but so far I have been unable to find the hardware specifications for these. Are these IO port bound or do these interfaces emulate keys ?
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ZX80 Pacman opening screen
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1024MAK
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Re: ZX80 joystick port

Post by 1024MAK »

Kempston is a joystick interface that is a Spectrum "standard", but often they came with a ZX80/ZX81 sized edge connector.
The ones with such a connector can be used on ZX80's and ZX81's as well as Spectrum's.
They are read via IN A,31 in machine code (port 31 dec) but often have very basic port decoding.

Not fully sure what Paul means about "Sinclair" joysticks, but probably means keys 1,2,3,4,5 or 6,7,8,9 and zero. This is an official standard on Speccies (like Interface 2, Amstrad +2, +2A, +2B and +3). Sinclair joystick ports map joysticks to one of these two groups of keys.

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gertk
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Joined: Sun Oct 14, 2012 9:09 pm

Re: ZX80 joystick port

Post by gertk »

They are read via IN A,31 in machine code (port 31 dec) but often have very basic port decoding.
I had setup a debug function on any unknown IO ports but when I selected Kempston it did not trigger once..
Have to dig deeper I guess or just add some code to emulate the cursor keys with the joystick.
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Re: ZX80 joystick port

Post by RWAP »

I would guess the joystick implementation comes from the fact that Paul sells a ZX81 emulator on a Spectrum ROM cartridge - so I guess the support is for the Kempston interfaces (for the Spectrum, or for the ZX81 if you can find one the right width), or for the Sinclair joystick ports built into the ZX Interface 2 on the Spectrum.
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