CURRENT SCHEMATIC

[exxos]

This is the current schematic for the new STF design.

This still needs checking against the STFM schematic for mistakes.

STF-min.png (1.19 MiB) Viewed 6874 times

Also see here https://www.exxosforum.co.uk/forum/viewt ... ?f=19&t=15 as the RS232 circuit has been replaced totally.

[tfhh]

Hi,

This is the current schematic for the new STF design.
This still needs checking against the STFM schematic for mistakes.

Looks very cool. And I see, you´re also a friend of Eagle

Jurgen

[IngoQ]

Wow...

[keli]

How does the RAM circuit select between the upper and lower half of its 32 bit data bus? I looks like you've just connected each pin of the 16 bit bus twice.

[exxos]

How does the RAM circuit select between the upper and lower half of its 32 bit data bus? I looks like you've just connected each pin of the 16 bit bus twice.

Connects up the same as a 4 MB 72 pin simm.

[keli]

Connects up the same as a 4 MB 72 pin simm.

Yeah, I never understood those hacks either. I see you used to have a 72 pin SIMM kit available as well (and I think I might have asked a similar question before.) If I'm not completely wrong, 72 pin SIMMs do not have ways to target individual bytes. How does updating or reading either one (only CASxLow or CASxHigh asserted) or even two bytes out of available four bytes work?

Since you've produced the 72pin SIMM kits I don't doubt it works, I just can't understand exactly how it works

[keli]

I think I get what I had wrong. The pinout on pinouts.ru is different. It has A10 and A11 where other pinouts list CAS2 and CAS3.

Mystery solved!

Edit That previous pinout was something called "72pin simm with ECC". It's not the first time I've been fooled by the wrong diagram. The correct pinout for a 72 pin simm is: http://pinouts.ru/Memory/Simm72_pinout.shtml

[exxos]

Yeah, I use that site mostly. I have seen sites with wrong pinouts. But IIRC, there are some simms used in some odd PC's which do have odd pinouts.