RP2040 replacement for IPC ?

[Peter]

It would be quite simple to use a spare PIO to define a SRAM chip-style interface.

As for implementing Q68 graphics that way: I'll believe it when I see it.

Such interface means at least: Two data strobes, R/W, chip select, 16 data lines, 21 address lines for the VRAM area itself - and to make actual sense, it would require even more lines, so no external logic chip is required for decoding. Not enough pins free for that, even if internal memory was large enough. Mind you: As soon as an extra programmable logic chip is required, one can use a low-end FPGA, which does whole video task, and the cost saving idea by using a µC becomes pointless.

[Nasta]

I think the target was something like a SGC, like it was for the original Aurora. In that case the bandwidth is far lower, not evenb 2Mbytes/sev as it emulates the original 68008, and needs in theory up to 256k of screen RAM, but these days not nearlčy all Aurora resolutions make sense, so 192k is enough, especially as the allocation of that RAM can be much more optimal because for Aurora, the bitmaps were always the same, the difference was how much of it was visible. So, it was 1024x1024 in 4 colors, 1024x512 in 16 colors, and 512x512 in 256 colors. These days, up to 1024x768 in 4 and 512x284 (based on 1024x768 monitor timing) in 256 colors is fine, needing 192k. 640x480 in 16 colors (although 16 colors was never a QL thing, we could use 8 as a template) needs 150k.

[Popopo]

In case it helps (if you haven't already seen it) there's a partially commented disassembly of the 8049 on my site:

https://www.dilwyn.theqlforum.com/qlrom/ipc8049.zip

May be of some help to you to know what the code expects by way of timings and signals, maybe.

Hi!
The new link is: https://dilwyn.theqlforum.com/docs/disassem/ipc8049.zip
Today I was studying this IC in order to replicate it partially.
Thanks

[Popopo]

...you'll also find a beautifully comprehensive description of the ULA/IPC 'interface' in the Minerva ROM source, thanks to our friend Mr Reeves

Hi Martyn,
Trying to find this information,
Which file contains it?

There are huge number of files. Actually I am interesting about how to read keyboard once keys are pushed, and how the system is aware of reading the input from this IC.
The only thing I have understood by the information is the keymap matrix and that the 8049 is in charge of scan the keyboard.
Where it write the code? In RAM? which lines does it use?

Thanks,

[martyn_hill]

Hi Popopo!

The files within the Minerva source-tree with most relevance to IPC/PC ULA communcations would be:

ip_init_asm
ip_kbrd_asm
mt_ipcom_asm

and the short section headed 'pc_ipcwr' in:
inc_pc

Good luck!

[dilwyn]

In case it helps (if you haven't already seen it) there's a partially commented disassembly of the 8049 on my site:

https://www.dilwyn.theqlforum.com/qlrom/ipc8049.zip

May be of some help to you to know what the code expects by way of timings and signals, maybe.

Hi!
The new link is: https://dilwyn.theqlforum.com/docs/disassem/ipc8049.zip
Today I was studying this IC in order to replicate it partially.
Thanks

Oops, thank you for the correction Popopo.

[RalfR]

640x480 in 16 colors (although 16 colors was never a QL thing, we could use 8 as a template) needs 150k.

It would have been good if a driver had existed for this resolution; then we could have potentially had 16 colors on the Atri TT without additional hardware. It's a real shame.