Sinclair ZX80 / ZX81 / Z88 Forums

300ns Sounds reasonable to be able to use the Pico RAM as ZX81 Memory Expansion. Do you think this might work? My Idea is having the Pico to supply the Zeddy memory and have it doing SD Card reading and writing directly from Pico memory for loading, saving, supplying alternative ROMs etc. My origin...

Got the version 2 PCBs back yesterday and the new io-port based design works great. (Currently using port 0x1F for control, 0x0F for data, but I can match any port with the least significant four bits high). The new feature (reset Z80 from the io board) works as well. https://pbs.twimg.com/media/FbH...

Yes, I plan to release the source code soon. I'm currently working on a new (and hopefully definitive) version of TF79, several modifications and improvements. As soon as I finish writing the documentation I intend to release it here. Excellent. I look forward to it. It kind of blew my mind how res...

Wow! I stumbled on ToddyForth 1.0 earlier today and was impressed... and then discovered there's been a lot further work done since then! Are there any plans to resource source code for ToddyForth-79? If not, would you consider adding a mechanism to add custom io implementations for load/save/list/p...

Got as much mileage as I could out of the original v1.1 PCBs. Send out new v2.0 ZX-PICO-IO designs for fab today. Featuring: - right-side-up connectors - IOPORT rather than memory mapped interface (hw address decoder matches on IORQ + A0..A3 HIGH + nRD or nWR, PICO sees A4..A7 for further decoding/r...

It works fine in emulation. After my last round of cleanup LR2 now works on the ZX81+38 loaded via the zx-pico-io... though I'm not 100% sure why. A couple other programs that failed to load also work now, so I'm suspecting the earlier code wasn't always getting the entire program copied over. The u...

https://sinclairzxworld.com/viewtopic.php?p=46313#p46313 Thanks! after loading you exit through a displayfile routine or...... you drop SP until at #556 and decrease frames by 1. I've been doing RST $08 DB $FF which seems to cleanly reset to the top of stack, etc and then fall into the display path...

In my ZX81 emulator i have 2 spots for load and save where I go to my own loader/saver. the source is available. Which emulator is that? Got a URL? My current USR invoked code is successfully loading most .p files I've tried so far, but there are some that I have loaded via the tape interface that ...

The remaining issue was indeed related to the PICO -- by default the firmware runs from SPI flash, XIP, and until the cache warms up it was failing to react to the bus quickly enough. Adjusting things to ensure the critical code and data was in SRAM and things work correctly from power up. And I'm n...

Thanks! That's a helpful thread. IY is clearly also a hazard, but provided I have SRAM "below" 0x4000, I can use negative indexing to access it, or I can use the print buffer as scratch space, or I can mirror the few variables the display routine needs if I move IY somewhere, so there are some optio...