ZXmore or the ZX80CORE follow-up

[siggi]

Andy, in general yes - you can execute code above 32k - even above 48k.
But there is a restriction for video driver code which is not possible - for machine code outside video during USR time there is no restriction at all.
There was a problem with z88dk I think using an own video driver above 32k used by siggi.
.

ahah, that will be why it crashed then, siggi wrote the zeddyfox using z88dk

All ZeddyNet-programs are written in C using Z88DK, because the ZeddyNet-libs are only available for Z88DK. Z88DK uses its own video-routine during ZX81 SLOW mode, because the original ROM video routine uses the IY register, which is used in many Z88DK-libs and also the ZeddyNet libs. Thus the Z88DK video routine does not use this register. So when a ZeddyNet program is running above 32K, the Z88DK video routine is also above 32K (except when using dirty tricks )

Siggi

[martinjharvey]

Thought I'd give this a try to see if it would clear up the graphic/display issues that I'm experiencing with my ZXMore....

Anyway, if I touch the X1 ceramic resonator with my finger for about two seconds, it locks on to the correct frequency.
Mark

Now when I power on, the ZXMaster menu is flickering and the rainbow colours start leaping out from the sides of the on screen text and menu border. I found, like Mark, that if I touch my finger on the blue 3 pin crystal/filter in position X1 on the PCB, for about 2-3 seconds, all of a sudden everything on screen becomes stable and clear......beautiful monochrome

The screen then remains stable and colour/flicker free even after resets, but the minute I turn the power off then turn it on again the display reverts to being all over the place until I tickle X1 again

Is X1 faulty or prone to being faulty? I've no real equipment to test this other than a multimeter, so should I just replace it?

Mart

[PokeMon]

I am not sure if a crystal can cause the grey lines between the characters as they are steady and its not just a jitter.
Did you use the double socket for the 74AC86 and could you check if it is correctly pressed in it's place ?
Could you check R16 as 100k resistor ?
I could send you a resonator for free to check if a replacement would help.

[martinjharvey]

Thanks Karl, I'd appreciate it if you could send me a resonator to try as I cant seem to find any at 6.5mhz

I've checked R16 and it is 100k resistor. I used the double sockets as you suggest in the build instructions. I used them for IC10 and IC12 as shown on the component diagram marked with the *** in the build manual and they are all seated correctly.

Touching the resonator didn't fix the grey lines between characters, but to be honest if swapping the resonator cures the colour/flicker I'm getting then I'm happy

PM if you need my address details.

Thanks

Mart

[PokeMon]

Hi Karl,

I've tried uploading some photos of my ZXmore but the board says the limit for attachments is reached. So instead I've zipped them up for download here
http://www.martinjharvey.com/ZXmore.zip

I've checked the capacitor that you mentioned and it appears to be the correct one installed in the correct place according to your build instructions. I am experiencing a colour effect when using my ZXmore on a 32" Samsung but on a cheaper Bush TV (maybe 14" screen) the display is stable yet the entire screen seems shifted over to the right by about an inch. Not sure whats happening but this occurred before the update and is still present now. The pictures I've taken show it better than I can say it

The colour/rainbow effects were difficult to capture but they can be seen on the close up of the ZXMaster instance that I took.This effect is now not present in the ZX81/80 instances as it was prior to the 1.7 update, just the ZXMaster instance. I have replicated this effect on my actual ZX81 that has your ZX8-CCB installed, so it could be some sort of sync issue. I can tweak it out of my ZX81 and get a stable clear picture on both TV's however using the ZX8-CCB trimmers.

One other thing I've noticed is that when I enter an instance, say ZX81 instance 1, the inverted K cursor has the K shifted to the bottom of the inverted square(photo in zip). The same is also true when entering a program and the inverted current line cursor is the same! This does however correct itself if I DS-C the instance for compatibility mode.

Apart from these niggles everything else is groovy

Mart

PS. You were right, I did have the full kit from you

Hi Mart,

I just saw your pics today and it is absolutely curious to me. Even the movement of the scalene counter. This is hardcoded and there is no difference if your press DS-C or use directly. The only thing I can imagine is that there might be a problem in your CPLD - so I would ship a new CPLD for you as well and see if this changes something. I even did modify my ZX81 to 3.25 MHz hardcoded but this does not affect the scanline counter to give it an offset. In theory it would be possible that the r/c timing combination of R26 and C9 is wrong and let the scanline counter start too late but then it would be the same for every ZX81 instance without ZXmaster - there is no difference.

Likely it is possible that the CPLD does some wrong things or give spikes to the scanline counter or additional scanline counter reset or pulse to the output signal on sync which might be interpreted as either colour information when present during back porch and could produce the small lines as well. The point is that it could disappear when there is an interdependency with i/o addresses used, setting nmi counter or similar and present during ZXmaster running in the background only.

I would prepare a small package for you with a new CPLD with the latest version, a new resonator and some capacitors and resistors you may use to test something. And yes - I should have your address in paypal or sellmyretro, I think.

[martinjharvey]

Thanks for your help Karl

[PokeMon]

So here's the whole screen. It's an old Dell 2001FP which I've used for ZXMORE in the past. Just looking at the photo again, it's interesting that the faint grey lines don't appear around all characters (eg. the numbers don't seem to have them, nor do the punctuation chars). It's not something to do with the changes for the upper/lowercase support?

Coming back to this issue with the small lines between chars I am pretty sure this is an issue shown on full hd displays only. CRT should work well also displays with lower resolution. My plasma TV with 1024 horizontal pixels doesn't show this small grey line either. This is a timing mismatch between activating inverted chars which are used in the 128 chars charset (ASCII) to use the existing display routines. Chars upwards $40 are stored inverted and shown inverted which give the normal look. So all letters are involved. This is a delay of about 15-20ns which is about 10% of a ZX81 pixel or about 20% of a TV (CRT) pixel and this way not visible.

If you have 1920 Pixels in about 54us this is about 70-75% of a HD pixel so probably visible. I am not sure if there is an more or less easy workaround but I will think about it. So using a lower resolution TV shouldn't show up these small lines.

[Lurch666]

Announcement - there is a required hardware change for the next release of ZXmaster (control software for ZXmore).
A small 47pF capacitor is needed between pin 27 (/M1) and pin 29 (GND) for timing purposes.
See the picture below.

So I've just finished building my ZXmore.I took my time and over several days have built it using the instruction but I have messed up somewhere and it's not working properly.
I'm using a CRT composite monitor with all the jumpers set as stated.

I'm getting a blank white screen that flickers with no cursor or text.The LED is off.If I power off then on sometimes the LED will change colour without my changing the rom switch.
Changing the ROM switch does produce the correct colours though.It looks to me like the system isn't initialising correctly.Checked soldering and chip legs but can't see where I've gone wrong.

Do I need to add the capacitor as mentioned above as it's not mentioned in the manual.Have also looked through this thread and tried removing IC22 and 24 but this made no difference.

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Lastly thanks for making this kit.It took me back to when I built my first computer (ZX-81) back in the 80's.
My soldering skills are way better now but when I made the zx-81 at least it worked.It was a simpler build though.

[PokeMon]

Congratulations, your work looks very clean.
I think (and hope) it is just the jumper on the io base address (J12) which should be moved from A7 to A3.
As you order was this month you got the release 1.7 burned in and due to compatibility reason the io address changed.
This can be configured in the upgrade utilities but usually fixed in the flash rom.
Probably this is not documented good enough in the construction manual - do you have the user manual as well ?

[Lurch666]

I had a quick look in the user manual but must have missed that bit.Will read it all now.

Changing the jumper still gives me a white screen with nothing else.With the rom switch on 0 if I press reset the screen flickers then fades to black.
If I put the rom switch to anything else the screen flickers but stays white.The LED still changes to the correct colours.


EDIT:Looked through the 1.7 user manual and still can't seem to find where it says I should use the jumper at A3 instead of A7