[Coco] DE-1 Expansion Board Project - I need a suggestion

[Steven Hirsch]

On Mon, 14 Jun 2010, sales at gimechip.com wrote:

> Hey folks:

> I've finished the 1Mx16 (2-meg total) SRAM design for the DE-1 Expansion 
> board. I've also included the Analog Joystick circuitry as per Gary's 
> request.

I think the CoCo community should elect you honarary hero!

> I had originally intended to include a battery backup for the SRAM. 
> However, at present, I have removed it from the design. The reason being 
> that the ISSI RAM chip specifies a 3.3V power source in order to operate 
> at 8nS, which is important to the CC3FPGA project. The battery backup 
> circuit introduces sufficient voltage drop to force the SRAM to it's 
> 10nS access time. However, Gary suggested that I ask all of you if you 
> might want the battery backup circuit added. If I add it back to the 
> design, there would be a jumper to enable it, in which case the RAM 
> would have a 10nS access time, battery backup disabled would allow 8nS. 
> Let me know your thoughts.

I doubt a human would be able to detect a substantive difference in this 
case.  My vote is for including the backup function.

> P.S. - I might to a similar board for the Spartan, since I have one of 
> those - I don't have the DE-1 yet but I'm leaving Dad little notes 
> around the house: i.e. "Wouldn't you like to buy your son a DE-1?" - 
> hey, it worked when I was 7 :-)

Good luck with that one.  My folks told me to get a paper route... 
(Probably dates me some, doesn't it?).



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