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CURRENT SCHEMATIC

Posted: Tue Sep 05, 2017 4:39 pm
by exxos
This is the current schematic for the new STF design.

This still needs checking against the STFM schematic for mistakes.

STF-min.png
STF-min.png (1.19 MiB) Viewed 2557 times

Also see here viewtopic.php?f=19&t=15 as the RS232 circuit has been replaced totally.

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 8:21 am
by tfhh
Hi,
exxos wrote:
Tue Sep 05, 2017 4:39 pm
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

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 8:52 am
by IngoQ
:shock: Wow... :)

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 12:53 pm
by 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.

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 4:27 pm
by exxos
keli wrote:
Wed Sep 06, 2017 12:53 pm
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.

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 6:38 pm
by keli
exxos wrote:
Wed Sep 06, 2017 4:27 pm
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 :)

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 7:02 pm
by 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

Re: CURRENT SCHEMATIC

Posted: Wed Sep 06, 2017 9:24 pm
by 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.