SD card reader for ZX81

[1024MAK]

The main ZXpand+ listing is here. Register on the site and then use the “Notify When Back in Stock” button.

Mark

[McKlaud]

There is also renewed ZX1541 on the market which works with any SD2IEC well.

[crrush]

Will it be good for zx80?

[diskman]

There is also renewed ZX1541 on the market which works with any SD2IEC well.

I ordered my ZX1541 a few weeks ago. It should arrive in a week or so! I plan on using one of my many real 1541 drives. lol. I have an SD2IEC and PI1541 available, but feel that actual floppies on the T/S 1000 would be awesome. I need to do a 16K internal mod on my main TS1000 before I jump into the ZX1541 interface.

[1024MAK]

The ZX1541 that I ordered arrived on the 5th of February, but I have not yet had any time to play with it

Mark

[Lardo Boffin]

A ‘spand has just come up on eBay but will doubtless go for silly money.

https://www.ebay.co.uk/itm/ZXpand-for-Z ... %7Ciid%3A1

[Spinnetti]

The expansion options are awesome, but my dream is to have what looks like a microdrive but is really an SD reader. I'm on KS2 for a Next, but still like the old hardware to run my code on just to show myself it can.

[sittner]

Hello community,

Some time ago I've developed a tiny file system and a SD card adapter for the ZX81. The goal was to avoid a extra processor like ATTINY and only depend on hardware that was already available back in the 80's (apart from the SD card itself). The project comes back to my mind because I've started some retro crafting with friends.

Maybe it will be of interest to one of you: https://github.com/sittner/tinyfs

There are some tests pending for an issue with HR graphics, which i hope to finish in the next few days.

Kind Regards
Sascha

[siggi]

Hello community,

Some time ago I've developed a tiny file system and a SD card adapter for the ZX81. The goal was to avoid a extra processor like ATTINY and only depend on hardware that was already available back in the 80's (apart from the SD card itself). The project comes back to my mind because I've started some retro crafting with friends.

Maybe it will be of interest to one of you: https://github.com/sittner/tinyfs

There are some tests pending for an issue with HR graphics, which i hope to finish in the next few days.

Kind Regards
Sascha

Hi Sascha
currently your diode D2 always enables the ZX81-rom during refresh. But then you cannot read HIRES data from ram, which also needs to be enabled during refresh (at it's own address). You should enable your own rom only during READ cycles at it's own address and the ZX8-rom only during REFRESH cycles at it's address (for access of the character generator in rom).
R5 is NOT needed for HIRES!

And to avoid a possible timing problem, you should not enable the ram's /OE and /CS at once. Enable /CS by the address decoder, /OE by (/RD AND /RFSH)

HTH Siggi

[sittner]

Hi Siggi,

Many thanks for the suggestions.

I have already fixed the HRG issue (https://raw.githubusercontent.com/sittn ... e/zxsd.pdf). Now I've completely disabled the internal RAM/ROM and took nRFSH into account for generating the CS signals. The fixed PCBs are on the way and I will test them when they arrive.

R5 is a relic from an old circuit diagram and will be removed in the next revision.

You are right about the RAM OE. I am not happy with that either, but I ran out of gates and did not want to restructure the entire board to add just one AND. I like to try a diode logic solution (https://raw.githubusercontent.com/sittn ... e/zxsd.pdf). I don't really like that, but seems to be better than the old situation. I will patch the new boards and run a test....

Kind Regards
Sascha