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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Fwapp
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Re: ZXblast - ZX81 memory extension plus USB

Post by Fwapp »

I don't have a WRX rampack, but I do get the same behavior with my blast, keyboard does not respond and my "ship" goes left and fires continuously.

Does memory configuration make a difference - mine is set standard, 0-16k ROM, the remainder RAM.
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000
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mrtinb
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Re: ZXblast - ZX81 memory extension plus USB

Post by mrtinb »

Looking at the code it seems to assume a ZXpand on port E007, and some how this corrupts reading the keyboard.
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon »

Jose_Leandro wrote: The blinks returns when , for example, I load a program and zxblast takes control of zx81. When zxblast load the program and return to normal mode, the program I load run witout problems
The video timing could be slightly different when ZXblast config/or load function active. This should not result in problems but CRT TVs accept looser timings than some LCD TVs with special chipsets. I will check that out. I have no idea what you mean with blinking. Could you post a small video capture somewhere and a link ?
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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon »

mrtinb wrote:Looking at the code it seems to assume a ZXpand on port E007, and some how this corrupts reading the keyboard.
Indeed this is a strange io port. Normally the lower 8 bits are used (=07) and the ZXblast does use A3=0 for controlling hardware. This can be changed to A4-A7 (but need a utility to change io address) but this doesn't help if all address bits (A3-A7) are set to zero. In Sinclair style there is a minimal address decoding used with just one io line (low aktiv).

A0=0 read keyboard/switch on nmi
A1=0 switch off nmi
A2=0 printer control

Using E007 would conflict with many hardware when not full decoded addresses. :shock:
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Fwapp
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Re: ZXblast - ZX81 memory extension plus USB

Post by Fwapp »

mrtinb wrote:Looking at the code it seems to assume a ZXpand on port E007, and some how this corrupts reading the keyboard.
Ah, good to know :) - so the software is at fault not the blast, good stuff.
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000
Jose_Leandro
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Re: ZXblast - ZX81 memory extension plus USB

Post by Jose_Leandro »

Hi
PokeMon wrote:
The video timing could be slightly different when ZXblast config/or load function active. This should not result in problems but CRT TVs accept looser timings than some LCD TVs with special chipsets. I will check that out. I have no idea what you mean with blinking. Could you post a small video capture somewhere and a link ?
Yes, I know the problems with modern TV and older computer :-( . Sure it is a problem with the LCD tv but I want to share you this information

I put a video in my website:

http://hardware.speccy.org/img/MAQ01321.MP4

I used a ZX81 issue 1 with 2C210E ULA and BC548 composite video mod ( I quit all modulation circuit). Before that ( when zx81 have RF modulator) I did not found problems

In the end of video, you also can see a zx81 issue 3 board with 2C184E ULA and LM1881 mod ( to have "correct" tv signal). If I put the zxblast, I have the same problem.

Bye

José Leandro

P.D I use the scope and i don't found differences in video signal with o without zxblast
Jose_Leandro
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Re: ZXblast - ZX81 memory extension plus USB

Post by Jose_Leandro »

Hi

Tested in my 42" LCD tv. There is no problem with image so it's a incompatibility with small LCD

Bye

José Leandro

P.D well, there is a problem.... the image is too big :lol: :lol: :lol: :lol:
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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon »

Jose_Leandro wrote: Yes, I know the problems with modern TV and older computer :-( . Sure it is a problem with the LCD tv but I want to share you this information

I put a video in my website:

http://hardware.speccy.org/img/MAQ01321.MP4
This is crazy. :shock:
Did you make the "pop" sound yourself ? Or is it your TV ? :lol:
I will try to check this out.
The difference is maybe just one line (64us) in a frame.
You won't see the difference of 0.3% frame length on you oscilloscope but can be measured using a logic analyzer ...
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siggi
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Re: ZXblast - ZX81 memory extension plus USB

Post by siggi »

One of my LCD displays also blinks and plops at nearly the same frequency as shown in the video (I am living in the 50 Hz region of the world ;) )

Siggi
My ZX81 web-server: online since 2007, running since dec. 2020 using ZeddyNet hardware
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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon »

Well - I worked on the documentation and have a nice tool now to generate screenshots/hardcopies to build up the user manual. This might be useful for other applications and documentation too, especially for stuff not running on Emulators due to hardware requirements. But this week I have too much work to release the documents as some people in the working team got ill and I expect to have 10-12 hours working days this week. So tired when returning home.
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