Sinclair ZX80 / ZX81 / Z88 Forums

I never assumed it was limited :) How would you handle external hardware suppressing the internal ROM? Does the ula code provide and honour - for the sake of agument - ROMCS and RAMCS? C No, not yet. Following my own rules, the plan is to proceed as is to provide a 100% bus accurate simulation of a...

I believe that you'll have a much easier time when it comes to adding peripherals if the memory and IO systems get their own observers. Multiple memory observers need to be able to be present simultaneously. There's no 1:1 mapping of observers; the Z80 (which can do partial bus management but would...

Right, I can confirm that I had NMI timing slightly askew, which has fixed the scroller in the 25th Anniversary Demo. Based on random sampling, I think I also have something going wrong in my Z80's scheduling of read-modify-write (ix+d) type instructions, which I hope will ultimately explain the slo...

Thanks for that. Obviously the structure is very different from my emulator; my ULA code simply does this: if(NMIs are active) { set NMI line to same value as the HSYNC line; if(!halt line) set wait line to same value as the HSYNC line; else set wait line to inactive; } else set wait and NMI lines t...

looking at the youtube vid when doing the loading, see those vertical bars... Well that is classic symtoms of Hsync counter been reset by the Vsync ( which occur albeit very short, but a vsync signal non-the less during loading). re jig your code to reset the Hsync counter on IntAck (M! low and IOR...

I don't regard that as a hack - one could theoretically build a board with a big fat CPLD on it and remap discrete sections of ROM code at will. If you formalise your ROM patching fast loader as a hardware add-on you won't feel bad about it ;¬) Well it's implemented as a hack, sitting on top of my ...

There are - as far as I know - no ZX80 multi-loaders. There are three or four on the ZX81 that I'm aware of. Code freely exists to turn a .O or P into an audio waveform, so that could be a compromise. If you expect users today to endure 6 minute real-time load waits however ... well I don't think y...

I've found this not to be entirely accurate; of the files I have the .p/.81 files appear to be the data that would appear on a tape, with the filename missing. So, on a real ZX81 tape you'd see: long pause filename, with the high bit set on the final character file data short pause On a .p/.81 file ...

Unless you're aiming at spectrum emulation I would be inclined to forget about TZH. IMHO this is a bloated, unnecessarily complex format for storing ZX80/81 data. C The problem is that the structure of the emulator doesn't currently allow any route from the internals to the filing system, and I thi...

Progress: I've added ZX81 emulation; I think I have the test for resetting the line counter (and possibly for when the directly programmatic 'vertical' sync is output) wrong but some other timing error may be at play; I've added a fast loading option for software that uses the ROM routine — it shoul...