The TFMSX Is out of the bag...

[stephen_usher]

Is that different from the TI9928/29?

I know that you can hack 4164 chips (just adapting for the pinout) to act as video RAM for these.

See: http://www.primrosebank.net/computers/m ... mavram.htm

[stephen_usher]

Looks like a standard DRAM interface with two banks of RAM with separate CAS lines, with a third CAS line for expansion RAM.

Screenshot 2021-03-18 at 10.42.35.png

[arkadiusz.makarenko]

If you need ARM keyboard firmware, I do have some experience with those already ;)

Wanna use the same arm chip? I can just copy paste the circuit over to the MSX

Cheaper f730 with exactly the same circuit would be more than enough

[terriblefire]

Looks like a standard DRAM interface with two banks of RAM with separate CAS lines, with a third CAS line for expansion RAM.
Screenshot 2021-03-18 at 10.42.35.png

Yes. So to be more efficient i'd need SMD DRAM thats 8 bits wide or 4 bits with a dual CAS.

EDIT: in other words 4164 would make the problem worse as i want fewer chips and SMD rather than more chips.

[stephen_usher]

I take it that you have the V9958 datasheet: https://www.google.com/url?sa=t&rct=j&q ... a7lGv88dwA

You could just use the CAS lines as extra address lines and add some logic to do the real CAS on the DRAM by ORing them and then use a bigger RAM chip.

[terriblefire]

I take it that you have the V9958 datasheet: https://www.google.com/url?sa=t&rct=j&q ... a7lGv88dwA

You could just use the CAS lines as extra address lines and add some logic to do the real CAS on the DRAM by ORing them and then use a bigger RAM chip.

Yeah. I'm just looking for a nicer part than the 41464 through hole jobs. I'm a long way into the design.

EDIT: i dont use a chip without checking a its docs into my private repo. ;)

[stephen_usher]

Surely any larger 8 bit DRAM will do, and just tie the extra address lines to zero.

I s'pose you could create an SRAM interface if you really wanted. Maybe have the VRAM on a daughter board so that you can fit whatever RAM board you like on there with the relevant logic? It would make the main PCB simpler and you could change the VRAM board as and when different RAM chips become available.

[terriblefire]

A bigger DRAM chip thats 8 bit is what i'm asking about. I dont know of any.

SRAM and solutions involving logic defeat the purpose.. Must take up less board space than 4 x 41464s.

The research i already did indicated that only EDO sims have these chips on them and they're pretty rare. Thats why i asked.

[terriblefire]

Also you can all blame this man for the TFMSX...

https://www.twitch.tv/banjoguyollie

He basically said..

x6UcUnmtQTNZ.gif

[stephen_usher]

I take it that you have the V9958 datasheet: https://www.google.com/url?sa=t&rct=j&q ... a7lGv88dwA

You could just use the CAS lines as extra address lines and add some logic to do the real CAS on the DRAM by ORing them and then use a bigger RAM chip.

Yeah. I'm just looking for a nicer part than the 41464 through hole jobs. I'm a long way into the design.

EDIT: i dont use a chip without checking a its docs into my private repo. ;)

Just a thought. There are quite a few SMD 16bit DRAM chips available at lowish prices. Use one of those and just not use the upper 8 bits? I guess that they're bigger than a single 41464. Also 3.3V, which means more circuitry.

e.g. https://uk.farnell.com/integrated-silic ... dp/2901170