ZX80/ZX81 core [new]

[slingshot]

Just for exercising FPGA programming, I've created a new ZX80/ZX81 core based on Sorgelig's much improved T80. Feel free to try out:
https://github.com/gyurco/ZX8X_MiST

[RobeInie]

Thanks !!

I will try next week, when I arrive at home,
Nice to see turbo loading in features !

[squid4]

Great to see the ZX81 getting some more love! What is the rom supplied with this, doesn't look like a UK ZX81 one to me (actually looks to be ZX80 only). Tried using an original ZX81 ROM but it doesn't work - from here https://k1.spdns.de/Vintage/Sinclair/80 ... ZX81/ROMs/

Update: Figured it out, start it, F12 change to ZX81 and 16K then select reset. Starts as ZX81 then. Doesn't save the settings so it needs to be done each time it is started. Can it default to ZX81 16k instead of ZX80? Tried Mazogs and it loads instantly and works great! Also nolimits.p demo works well.

[DanyPPC]

Thanks for this new core

[slingshot]

Figured it out, start it, F12 change to ZX81 and 16K then select reset. Starts as ZX81 then. Doesn't save the settings so it needs to be done each time it is started. Can it default to ZX81 16k instead of ZX80? Tried Mazogs and it loads instantly and works great! Also nolimits.p demo works well.

You can save the setting as in other cores: press RIGHT at the OSD, then choose "Save settings".

[desUBIKado]

Thank you slingshot for your core. It's great see new cores for MiST

I have tried your core a little and I've saw a visual issue with the first lines of the screen

M800_20180817_212303.jpg

M800_20180817_212045.jpg

These images are on 15 KHz RGB output, but I get the same result with VGA output, on 50Hz or 60 Hz, with my Mistica FPGA16.

[slingshot]

I have tried your core a little and I've saw a visual issue with the first lines of the screen

There's a 2 clock cycle skew in the HSync counter at the first line, which I don't know if it's a problem with the T80, my ZX81 implementation, or it's just there with the original hardware, too. For example, it is hardly noticeable on my TV, but with scandoubling it's very obvious.
Also there are conflicting informations on the net when the HSync counter should be synchronized, Grant Searle's site says it's synced to INTACK, but other places says it's synced to VSync. So if somebody has more information about it, please share. Currently it's synced to INTACK.

[Sorgelig]

if it's a problem with the T80,

Apply my recent DI_Reg fix from SAM Coupe core - it may help.

[slingshot]

So released a new version, with the HSync signal shifted by two clock cycles, which seems to solve (or hide?) the problem.
Also added 64k RAM pack support, so the great remake:
https://problemkaputt.de/hero.htm
can be played!
If it is not displayed with scandoubler, try setting the frequency to 60Hz.

[squid4]

Last good one on my Sony CRT 15khz was zx8x_20180815.rbf. Any after that the picture is very dark.

[slingshot]

Last good one on my Sony CRT 15khz was zx8x_20180815.rbf. Any after that the picture is very dark.

I fixed this (at least it looks good on my TV). Please try today's release.

[squid4]

slingshot, Wow! you've fixed it. Skew problem, that also affected the older core I worked on, has been fixed and the video looks perfect on SCART - looks better than my real ZX81!

With your permission I'll replace the old core on the official Mist website with this core.

[slingshot]

Of course you can put it on the main MiST binaries site.

[slingshot]

Released a new version:

- Joystick support (keys 67890)
- AY sound chip (with ZON X-81 compatible ports)

https://github.com/gyurco/ZX8X_MiST/blo ... 180825.rbf

[NML32]

Nice job on the core.
Thanks for adding joystick support.

[desUBIKado]

Glad to see the first line issue is fixed. Great job.

20180826_113853.jpg

[slingshot]

Thanks to Sorgelig, he fixed the NMI cycle of the T80, so now the core is cycle perfect. Still has some hsync shift in FAST mode (only in 2 lines), but this seems to be present on the original machine, too.
New release:
https://github.com/gyurco/ZX8X_MiST/blo ... 180828.rbf

[slingshot]

Just added CHR128 character board support.
Changed the releases structure, new release is here:
https://github.com/gyurco/ZX8X_MiST/releases

[DanyPPC]

Many thanks for this update !