Lambda 8300 ULA

[gozzo]

No, a ZX81 ULA wont work in a Lambda, or the other way round, there appears to be no area of the Lambda ROM that has the character bit patterns(well, i cant find them!)unlike the ZX81 ROM, which has them at the top 512 bytes..only possible conclusion is that they are stored elsewhere and as no other ROM, the Lambda ULA must also have a ROM section in it somewhere!!!

[gozzo]

May be possible to make an adaptor board to take a ZX81 ULA plus extra EPROM for the character patternss, plus its decoding circuit, also the Lambda has crude sound capabilities, not sure how this is achieved!

[1024MAK]

Pictures from mine:-

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"ULA" C4005

(246.84 KiB) Downloaded 1253 times

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Z80 CPU

(347.67 KiB) Downloaded 1253 times

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ROM AMI 8444FC
10830-21103-01

(188.69 KiB) Downloaded 1253 times

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SRAM TMM2016P-1

(425.92 KiB) Downloaded 1253 times

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Board

(467.3 KiB) Downloaded 1253 times

Mark

[nollkolltroll]

There is great documentation on the Lambda in a section at http://problemkaputt.de/zxdocs.htm, including where font is stored and sound capabilities.

[mrtinb]

Are you sure it's the ULA at fault?

I havn't measured the Lambda 8300 yet. 1st project is to get the ZX81 running again.

May be possible to make an adaptor board to take a ZX81 ULA plus extra EPROM for the character patternss, plus its decoding circuit, also the Lambda has crude sound capabilities, not sure how this is achieved!

What I've read, the Lambda will work with a ZX81 ROM, but not with graphics or pseudo graphics. Somehow they must be quite similar.

Martin

[mrtinb]

Maybe some of the creators of the emulators know how the ULA in Lambda 8300 is different from the ULA. How the char ROM is connected to the rest of the ULA, or even how similar the ULAs are.

[olofsen]

Emulator code for the ZX81 also runs the Lambda, with the exceptions mentioned by gozzo: sound and the character bit patterns. The ZXmore runs the Lambda, if the I register is set to for example $3e (normally 0) to point at character bit patterns loaded in RAM at address $3e00. This suggests that a ULA replacement board could indeed work, with logic added to get the bit patterns from another ROM instead of the first pages of the Lambda ROM.

[PokeMon]

I didn't try out that.
Did you try flash rom as well or has to be RAM ?

[olofsen]

The flash ROM should also work, but I haven't tried it; the area $2000 - $3000 is also used to store colour information (http://problemkaputt.de/zxdocs.txt). By the way, ports $f5 and $f6 seem to be used by the printer (http://sinclairzxworld.com/viewtopic.php?f=18&t=1681) so printing could have spectacular effects

[PokeMon]

The flash ROM should also work, but I haven't tried it; the area $2000 - $3000 is also used to store colour information (http://problemkaputt.de/zxdocs.txt). By the way, ports $f5 and $f6 seem to be used by the printer (http://sinclairzxworld.com/viewtopic.php?f=18&t=1681) so printing could have spectacular effects

Okay - it shouldn't be a problem to change the i/o address with the install program (ZXmorexx.p) to a different address line than A3.