ZXmore or the ZX80CORE follow-up

[Andy Rea]

oh i did not know you could power it via the usb

yes i was wondering about the address decoding sound card uses $CF, $0F & $DF, $1F so not sure what is happening.

Hmmm - that is maybe the problem.
I am using a configurable address which use A0 and A1 plus one other address line (AX) to be configured with A3-A7 by user.
Unfortunately it is not configurable now (only A7 possible) - but addresses $0F and $1F would conflict now with A7.
I think this is a bit unsual as addresses are normally low active used and $0F uses four address lines low (A4A7) which give much potential of conflicts.

Not sure what really happens as I am just writing to addresses $7C-$7F while the sound interface should be passive.

my soundcard ( home made of course ) is readable as well as writable, i will temporarily connect the /rd to +5v that way it can never put anything on the data bus i will report back when i try it.

regards andy



regards Andy

[Becky]

Has anyone given much thought to a case for their project yet? I had an idea earlier that an Acorn Electron care would be nice, I looked up how the keyboard was made- turned out it was individual key switches soldered to a pcb, so it would have been simple enough to cut the tracks on the pcb and rewire them in the zx pattern. I thought that maybe even there might have been a way to use the redundant keys for Extended Mode, Graphics Mode and Rubout. Sadly, it turned out that the ZXmore would be too wide for the electron. I thought about the Commodore 'Bread bin' style cases, but they are quite ugly and don't appear to have individual key switches.

Cheers,
Becky.

[Paul]

There was an acrylic case for the ZXCore and I am (trying) to offer something similar for the ZXMore.
I will have a prototype in a few weeks and will post pictures then.
kind regards Paul

[dinosaur]

Although I managed to revive my 33 years old ZX-81 (dead CPU (!), dead ROM, now both replaced and working), I must say that the ZXmore looks quite appealing... and even, amazingly sexy !

I'd consider buying one, but I got two "hard requirements" and also a wish.

The hard requirements deal with the level of compatibility with the original ZX-81. They are, in the form of questions:

• Is the ROM image used by the ZXmore 100% compatible with the ZX-81 ROM, i.e. are the usual sub-routines (maths routines, "print" and "input" routines, etc) that many (many of mine anyway) assembler programs call, located at the same address in ROM and using the same (or a smaller set of) registers ? The requirement here, is that any assembler program thrown at the ZXmore and making use of the original ROM sub-routines would work without a single glitch.
• Is the audio tape interface fully compatible with the ZX-81's ?... I.e., will fast loader programs such as the "Fast Load Monitor" run properly and successfully load/save programs from tapes ? For info, all my programs are saved using the Fast Load Monitor...

There's also the "wish", still in the form of a question: will there be a ZX-81 layout for the board (i.e. with the audio and power jacks and video connector on the left side of the board, instead of on the rear) ?

[Becky]

Dinosaur wrote:

, I must say that the ZXmore looks quite appealing... and even, amazingly sexy !

It's the white PCB, it looks amazing.

As I understand it, the ZXmore will use the open81 ROM. Can't for the life of me remember where I saw that, but there is a link below if you want to download it and have a play in your favourite emulator,

http://sourceforge.net/projects/sebasic/files/open81/

[PokeMon]

[*]Is the ROM image used by the ZXmore 100% compatible with the ZX-81 ROM, i.e. are the usual sub-routines (maths routines, "print" and "input" routines, etc) that many (many of mine anyway) assembler programs call, located at the same address in ROM and using the same (or a smaller set of) registers ? The requirement here, is that any assembler program thrown at the ZXmore and making use of the original ROM sub-routines would work without a single glitch.
[*]Is the audio tape interface fully compatible with the ZX-81's ?... I.e., will fast loader programs such as the "Fast Load Monitor" run properly and successfully load/save programs from tapes ? For info, all my programs are saved using the Fast Load Monitor...[/list]

Thanks for your interest in this project.
First the board is only existing in this ZX80 format and is not planned to fit in a ZX81 case.
Anyway it is to beautiful to hide in a black box - but this is my personal opinion only.

About the ROM's - you may use any existing ROM like even the SG81 (shoulder of giants with improved mathematics) or the original ZX81 as well. The reason why the default delivery is based on open81 is only a legal issue as the open81 was published under the GPL v2 licence and maybe used from anybody free without hurting any other's rights. It is in general binary identical with the ZX81 rom when you compare, so no problem. There is one modification in the NMI check routine which has to run double length as the ZXmore provides double frequency. This is the only changed thing (one byte difference only).

All audio routines are identically and I myself load programs via the audio port as well from PC (via soundcard). Most users will prefer the faster access on USB flash medium, I think. To be 100% sure it will load with Fast Load Programs I would propose to do a test. I don't know Fast Load Monitor - is it just software or hardware ?

Karl

[1024MAK]

Hi Karl

It would be helpful if you could document the one byte difference you referred to above in the next revision of the manual.

Mark

[PokeMon]

Yes sure - it is here, in the set slow/fast routine.

Code: Select all

;   Now test if this really is a ZX81 or a ZX80 running the upgraded ROM.
;   The standard ZX80 did not have an NMI generator.

        LD      A,$7F           ; Load accumulator with %011111111
        EX      AF,AF'          ; save in AF'

        LD      B,$11           ; A counter within which an NMI should occur
                                ; if this is a ZX81.
        OUT     ($FE),A         ; start the NMI generator.

;  Note that if this is a ZX81 then the NMI will increment AF'.

;; LOOP-11
L0216:  DJNZ    L0216           ; self loop to give the NMI a chance to kick in.

I changed register B from $11 to $22 as the ZXmore could run with double frequency to be sure not to miss the single NMI.

[dinosaur]

Dinosaur wrote:

I must say that the ZXmore looks quite appealing... and even, amazingly sexy !

It's the white PCB, it looks amazing.

Hehe, I was actually referring to the features, but the board sure looks good too !

[dinosaur]

Thanks for your interest in this project.

Thanks for this project !

Nostalgia is a strange thing which tends to affect human beings at our age... Your project arrives just at the right time to quench my nostalgia fit !

First the board is only existing in this ZX80 format and is not planned to fit in a ZX81 case.

Actually, I'm not planning to fit it into a ZX-81 case (the case of my own ZX-81 was trashed over 30 years ago, together with its totally worn out membrane "keyboard"...), but to fit it into an Indescomp box which got a mechanical keyboard, room for a power supply (and more: I currently got two Memotech modules in there, plugged via a bus expander provided with the box), and got the proper holes for all the ZX-81 plugs...

I find it a bit strange that you chose the ZX-80 layout for the board connectors, given many more ZX-81s were produced (1 500 000 or so) than there were ZX-80s (100 000), but it's of course your choice.

I'll just have to drill more holes in the Indescomp box, I suppose...

Anyway it is to beautiful to hide in a black box - but this is my personal opinion only.

Yes, it looks very nice, but electronics doesn't like much dust, and even less coffee drops, or short-circuits caused by a random metallic object falling down on it...
Plus, I want a proper keyboard (with numeric key pad as well), which the Indescomp box offers.

About the ROM's - you may use any existing ROM like even the SG81 (shoulder of giants with improved mathematics) or the original ZX81 as well.

That's great news ! Congratulations for a well thought-out design. I was kind of fearing that some specific hardware would have required changes in the original "drivers". I'm glad it's not the case.

The reason why the default delivery is based on open81 is only a legal issue as the open81 was published under the GPL v2 licence and maybe used from anybody free without hurting any other's rights. It is in general binary identical with the ZX81 rom when you compare, so no problem.

Yes, I gathered that the use of an Open Source equivalent was mostly a license issue, but another motivation for such a use could have been to modify the code itself over what the original ROM permitted.

There is one modification in the NMI check routine which has to run double length as the ZXmore provides double frequency. This is the only changed thing (one byte difference only).

As long as it's not an added byte (that would cause routine addresses to be modified), but just a changed byte, it's indeed of no consequence and an easy modification to do on the original ROM code.

All audio routines are identically

I was more worried about the bandwidth of the audio circuit: the Fast Load Monitor (FLM) program easily climbs into the 12KHz range, at the limit of what can be recorded on a good quality tape with a good tape recorder (FLM allows up to 5600bps, which, if to believe Shannon - I think we can ! -, would translate into a 11.2KHz bandwidth for a FSK signal such as the ZX-81's)...

If you used the same or better design/components as the ZX-81 did, it should not be a problem, but I need to ask.

and I myself load programs via the audio port as well from PC (via soundcard).

I doubt very much any existing emulator would understand/be able to deal with the FLM signal... Plus, I'm yet to find a ZX-81 emulator that would properly work on a modern Linux system.

Most users will prefer the faster access on USB flash medium, I think.

Well, before using the USB, I'll have to load the programs from the tape from the ZXmore... Kind of a Hen and Egg issue.

To be 100% sure it will load with Fast Load Programs I would propose to do a test. I don't know Fast Load Monitor - is it just software or hardware ?

This is very kind and considerate of you, and it's 100% software... However, I only have it on tape, so I can't send you a binary (not to mention the manual is written in French)... This said, if the audio circuit bandwidth of the ZXmore is of equal or better quality than the ZX-81's, and given the routines are the same, it should work just fine.