ZXblast - ZX81 memory extension plus USB

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Thu Feb 16, 2017 11:39 pm


wilco2009
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Re: ZXblast - ZX81 memory extension plus USB

Post by wilco2009 » Fri Mar 03, 2017 12:11 am

Hi, I would like to make two questions.

- I am trying to test "Hires" software, but almost all of "hires" games tested are not working. There are some incompatibility with them or I am doing something wrong?

- Do you plan to support tape files as T81 files?

thanks in advance.

rcade
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Re: ZXblast - ZX81 memory extension plus USB

Post by rcade » Fri Mar 03, 2017 4:04 am

Several I tested worked fine, but I think there are different kinds of Hi-res.

At least for the ones I tried (HRChess and HRInvaders) you have to change 8192-16384 to RAM in the ZXBlast interface. By default, it's ROM.

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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Fri Mar 03, 2017 5:36 pm

wilco2009 wrote:
Fri Mar 03, 2017 12:11 am
- I am trying to test "Hires" software, but almost all of "hires" games tested are not working. There are some incompatibility with them or I am doing something wrong?

- Do you plan to support tape files as T81 files?
I tried several programs with Hi-Res working.
WRX1K1.P vom Wilf Ritter
find here - the others should work fine, too.
http://www.user.dccnet.com/wrigter/inde ... khires.htm

Or the HRG programs from Mathias Swatosch:
http://www.swatosch.de/zx81/

There need to be done a NEW after loading the driver HRG16K.P before loading a user program like DEMO, SINUS or PIPES. Not sure why but didn't find the time to check this out.

If you find some programs do not work please list them with link to the program to download. Then I can test.


The other question, sure can you load .T81 files. These are identical to .P files in structure (as far as I know).
But I think I did load before. There are no file types explicitly associated except the .BAK extension used for instance backups.

wilco2009
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Re: ZXblast - ZX81 memory extension plus USB

Post by wilco2009 » Fri Mar 03, 2017 8:21 pm

Thankyou rcade and pokemon. I am understanding better Hires programs.

HRG programs from Mathias Swatosch.
These programs are working right now. I didn't knew that I have to load the driver before load the program.

WRX1K1.P and HRDEMO3.P vom Wilf Ritter.
Both are working fine.

UDG card mapped at 3000h
UDG-128 - UDG card with chr$ 128 scheme mapped at 3000h

Theese programs are not working. I understand now

Most of the old programs are working with a UDG card. Logically theese programs will not work without the UDG card.

Nevertheless, potentially your intarface could be able to emulate this type of cards. could be possible to make your interface compatible with this kind of cards?

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mrtinb
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Re: ZXblast - ZX81 memory extension plus USB

Post by mrtinb » Fri Mar 03, 2017 10:14 pm

For UDG you need a Chroma Interface
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

wilco2009
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Re: ZXblast - ZX81 memory extension plus USB

Post by wilco2009 » Fri Mar 03, 2017 11:29 pm

Thinking I understand now the problem to implement the UDG feature.

The problem is the same like the problem with the ROMs with no standard characters. To implement it, you should implement all the circuit to select the access to the character table during the refresh cycle, including the address selector, and the scanline and character counter. It is too complex.

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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Fri Mar 03, 2017 11:59 pm

Well ZXblast was not designed for using UDG.
I wouldn't say it is too complicate but need some extra parts to be realized.
UDG is not HRG - these are different kind of stuff.

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GCHarder
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Re: ZXblast - ZX81 memory extension plus USB

Post by GCHarder » Sun Mar 05, 2017 12:16 am

Converting a UDG program to run with ZXBlast ought not be too difficult, just make a ROM image and replace the normal character patterns with the UDG patterns then load that in ZXBlast. Next do a search of the program and find the instructions which change the character table vector, usually...

LD A,20
LD I,A

Just change $20 to 1E, just one POKE ought to do it.

Regards;

Greg

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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Sun Mar 05, 2017 12:26 am

Hi Greg,
it's not that easy. The character pattern from the video logic is read from the internal ZX81 rom. This is separated with resistors to let the ULA read the video patterns and overdrive the address bus during refresh cycles (I+R register). It is not possible this way to simply replace the video pattern (UDG) as it is read internally only.

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