About ZXPand...

Frequently Asked Questions about the Sinclair ZX81
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This is designed to be a simple set of questions and answers - please no general chit chat in here - keep it focused to help new users!
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Zac
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About ZXPand...

Post by Zac » Wed Nov 07, 2012 2:17 pm

I've bought a ZXPand and i'll receive it soon... i hope ! :D

I read the documentation and see :
Doc wrote: Support for all common software based hi-resolution systems.
What i'm supposed understand ?

I can play hi-res games and run hi-res animation/drawing ?

Thanks.
-=Zac

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sirmorris
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Re: About ZXPand...

Post by sirmorris » Wed Nov 07, 2012 3:26 pm

Hi-res in this case is WRX and similar schemes such as Math123's hi-res routines.

There is no support for user-defined character graphics (UDG), commonly known as CHR$16 or CHR$128.

There are some WRX hi-res games (like my own DarkStar2) but mostly games rely on the UDG schemes because they are less demanding on the processor.

HTH
c
--=== ZXpand+ ... A more moderner all-in-one upgrade solution for ZX81 ===--
* SD/MMC storage * 32K Hires-capable RAM * AY sound chip * Joystick port * Serial *
* BASIC enhancements - plug & play * Reset button * Auto-boot facility *

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Zac
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Location: Montpellier / FRANCE \o/
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Re: About ZXPand...

Post by Zac » Wed Nov 07, 2012 4:07 pm

Ok, if i understand, it's just a char redefinition and not a larger (better) screen resolution, right ?! :D
-=Zac

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sirmorris
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Location: oxon, uk

Re: About ZXPand...

Post by sirmorris » Wed Nov 07, 2012 5:23 pm

Zac wrote:Ok, if i understand, it's just a char redefinition and not a larger (better) screen resolution, right ?! :D
ZXpand enables the use of 256x192 'true' pixel-addressible hires. Or even more pixels...
--=== ZXpand+ ... A more moderner all-in-one upgrade solution for ZX81 ===--
* SD/MMC storage * 32K Hires-capable RAM * AY sound chip * Joystick port * Serial *
* BASIC enhancements - plug & play * Reset button * Auto-boot facility *

User avatar
Zac
Posts: 25
Joined: Wed Oct 31, 2012 10:28 am
Location: Montpellier / FRANCE \o/
Contact:

Re: About ZXPand...

Post by Zac » Thu Nov 08, 2012 8:21 am

Thanks Sir Morris, I'll make some test when i'll receive my ZXPand card ;)
-=Zac

gozzo
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Re: About ZXPand...

Post by gozzo » Fri Jun 21, 2013 12:08 am

After disabling the ZXpand with a CONFIG "X" command, is there any easy way to re-enable it without having to reset it ?

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sirmorris
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Re: About ZXPand...

Post by sirmorris » Fri Jun 21, 2013 1:34 pm

This should do it.

Code: Select all

; re-enable the overlay
    ld  bc,$e007
    ld  a,$b1
    out (c),a
Here are the hex codes for your favourite hex-code entering system:

Code: Select all

01, 07, E0, 3E, B1, ED, 79, C9
and in decimal for the pokers out there:

Code: Select all

1, 7, 224, 62, 177, 237, 121, 201
which are also this week's lottery numbers*.




*this is actually a lie
--=== ZXpand+ ... A more moderner all-in-one upgrade solution for ZX81 ===--
* SD/MMC storage * 32K Hires-capable RAM * AY sound chip * Joystick port * Serial *
* BASIC enhancements - plug & play * Reset button * Auto-boot facility *

gozzo
Posts: 444
Joined: Fri Jul 08, 2011 7:52 pm

Re: About ZXPand...

Post by gozzo » Fri Jun 21, 2013 6:37 pm

Thanks! (pity it couldn't just be done with a single POKE, though.. ;) ) Another little query..... any easy way of deactivating the zxpand RAM and both the zx ROM and zxpand ROM , so it could be fitted 'permanently' in my Fuller keyboard case, and any other external devices could deactivate the RAM and/or ROM as if it was a 'normal' ZX81???

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sirmorris
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Re: About ZXPand...

Post by sirmorris » Sat Jun 22, 2013 5:58 pm

I don't think it's easily possible to control the ROM overlay externally, that said I don't know of any other devices which disable the internal ROM. I'm sure people will enlighten me though :D

Ditto the RAM. It would entail listening to and obeying RAMCS - which would be tough as it also needs to control it. As ROM and RAM cs lines are designed to let external devices control the internal chips it's not really possible to have multiple external devices all mastering the same line. If you see what I mean.

C
--=== ZXpand+ ... A more moderner all-in-one upgrade solution for ZX81 ===--
* SD/MMC storage * 32K Hires-capable RAM * AY sound chip * Joystick port * Serial *
* BASIC enhancements - plug & play * Reset button * Auto-boot facility *

gozzo
Posts: 444
Joined: Fri Jul 08, 2011 7:52 pm

Re: About ZXPand...

Post by gozzo » Sat Jun 22, 2013 8:24 pm

The way I was thinking of doing it was adding a resistor of about 680ohm in series with the CS lines of the RAM and ROM chips of the zxpand, and feeding those points out to an 'external' expansion connector through diodes(cathode to chip CS), so if pulled to +5v would de-activate the ZXpand chips( but would it confuse the ZXpand processor? ), that's how it appears to be done in the ZX80 or ZX81 itself... as for deactivating the main ZX ROM (and RAM) as well, maybe the same way, fit a resistor in series with the CS line from the ZXpand and diode from this to the external ROM CS..??

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