Sinclair ZX80 / ZX81 / Z88 Forums

But what test does it apply? Is it any suitable io read so as to initialise direct programmatic sync, is it the edge of the vsync signal, is it any write that terminates direct programmatic sync or is it possibly even past the combined sync and applying a capacitor charge/timing test ala a CRT?

Having checked against one of his high-resolution demos, I think he may possibly just have mistyped, having meant to refer to vsync. Based on his code it looks like if the NMI generator is active then the directly programmatic sync signal, normally used for vertical sync, isn't output. Is that accur...

Sorry, some further questions, concerning the ZX81 specifically. Wilf's page asserts, under point 5, that if the NMI generator is disabled then an input on port fe "turns off the HSYNC generator (only if NMI is off)" and an output on port ff "turns on the HSYNC generator". Is it possible that all he...

Why don't you buy an oscilloscope or a logic analyzer to see what's going on ? So you are now working only in a virtual world. Anyway, have fun. :mrgreen: It wasn't the sole reason and the only 'simple' machine I physically own is a SAM Coupe. I'm also unwilling to buy anything much at the minute —...

To comment on these directly.. I'm sad I won't be seeing this for a while :( I'm interested in helping out with a Windows port though my time is pretty limited. Yes, sorry about that. I have a Windows 7 virtual machine so it's not necessarily a lost cause, I just don't really know where to start now...

So now there is Clock Signal Ha, not yet there isn't. I'm still expecting to discover such flaws in my design as to make the implementation entirely wasted. Most of the reason I started the project is that I want to gain a better understanding of how things operate at the electrical level, the coro...

It wouldn't be all that difficult at present. The sticking point is that I'm using blocks (the closure construct that Apple added to C and Objective-C in OS X v10.6) in order to thread hop for the purposes of running the emulation off the main thread without really having to do any work for myself. ...

If you'll indulge me... As I've said over on the hardware section of this forum, I'm working on a new emulator. It's structured quite differently from existing emulators, being based on the concept of completely sealed modules that communicate by signal wires — aping the original hardware rather tha...

Thanks for everything — I think you've answered all my questions perfectly and your website is really useful. I'm also quite glad to find out that the skew at the top of my emulated version of flicker-free Space Invaders is actually meant to be there, as I figured I had HSYNC close enough (in that m...

Thanks for the detailed reply — I hadn't realised quite how non-comformant the sync signals were. The PAL standard wants a horizontal sync to last for 4.7 ± 0.2 µs, but it sounds like on a ZX80 it'll last for about 6.2 µs? Though the ZX81 sounds like it's only just outside of the specified range. Pr...