Search found 54 matches

by kpalser
Mon Jul 01, 2013 12:09 am
Forum: Emulators
Topic: Help with ZX81 loading screen for new emulator
Replies: 18
Views: 3638

Help with ZX81 loading screen for new emulator

Folks, I have questions about the generation of the ZX81 loading screen. Apologies for the following long winded background: I have been writing on and off an emulator since 2010. It differs from many in that the module/class to display the video is driven only by the three state video output (1v wh...
by kpalser
Mon Jun 04, 2012 12:33 pm
Forum: Development
Topic: How the ZX81 NMI / sync works... my 10 points
Replies: 19
Views: 9590

Re: How the ZX81 NMI / sync works... my 10 points

Well, this thread does seem to have reached the consensus/acceptance that the HYSNC is always running. So, to reiterate my questions from yesterday: 1) About which cycle should the emulator be in the 207 cycle loop after at the OUT ($FF),A releases the 3 bit ULA character row counter (LCNTRL)? Which...
by kpalser
Mon Jun 04, 2012 2:00 am
Forum: Development
Topic: How the ZX81 NMI / sync works... my 10 points
Replies: 19
Views: 9590

Re: How the ZX81 NMI / sync works... my 10 points

Hmm - I am working on an extension for my video board - a sync generator to avoid loss of sync when ZX81 is running in fast mode. So I think in point no.4 you are maybe wrong. Sync generation is not permanently on and can (and will) be switched off when entering fast mode. PokeMon, sounds like an i...
by kpalser
Sun Jun 03, 2012 2:24 pm
Forum: Development
Topic: How the ZX81 NMI / sync works... my 10 points
Replies: 19
Views: 9590

Re: How the ZX81 NMI / sync works... my 10 points

Grant, Taking on board your findings regarding the free-running HSYNCs, for accuracy I reworked my main zx81 emulator loop to: - to incorporate the sync pulse for 16 cycles every 16 cycles into the 207 cycle loop - only have the cycle loop reset when INTACK would be generated in the central picture ...