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

[sales at gimechip.com]

Steven,
I'm laying out the PCB as we speak - actually I need to take a break and get 
a nap - Been working on it for hours - since I woke up yesterday. I hadn't 
included the battery as I received no response, but since I now have a 
response, I'll add the battery backup back in. I have included also a 40-pin 
IDE connector with the d0-d15 and a0-3 of the IDE interface connected to 
same signals of the SRAM - I am awaiting feedback to see if this is 
plausible. If if were not for you folks feeding me design ideas, I'd 
probably go bonkers sitting here at the house with nothing to do.

-John


----- Original Message ----- 
From: "Steven Hirsch" <snhirsch at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Tuesday, June 15, 2010 6:40 AM
Subject: Re: [Coco] DE-1 Expansion Board Project - I need a suggestion


> 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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