[sdiy] SRAM versus DRAM

[Dan Snazelle]

i know a lot of digital delays use the 2164 DRAM (peavey, electro harmonix and MXR digital delay) 
which is why before I saw the polyphony digital delay project which calls for SRAM (4k x 1 bit, 8 of them) I had thought DRAM was the way to go in a digital delay.

sadly the more i look into this the more I am seeing that there is a real issue...
if you want seperate In and out pins (which seems to make things a lot easier) than you need to use really small RAM chips and Use 
8 of them for an 8 bit DAC which is a lot of chips.

BUT if you want to use something that puts out 8 bits, you need to figure out the logic for properly switching between In and Outs


it sure would be fun to figure this out though!

thanks all



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----------------------------------------
> Date: Tue, 23 Jun 2009 21:19:11 -0400
> Subject: Re: [sdiy] SRAM versus DRAM
> From: jluciani at gmail.com
> To: subjectivity at hotmail.com
> CC: synth-diy at dropmix.xs4all.nl
>
> On Tue, Jun 23, 2009 at 8:15 PM, Dan Snazelle wrote:
>>
>>
>> in a project that calls for SRAM can you use DRAM instead?
>>
>> I know they are fundamentally different in that one type has to be refreshed but i suppose i do not understand
>> WHY the refresh is important
>>
>> in the case of a digital delay for example
>
> IIRC the DRAM refresh rates are on the order of micro-seconds not the
> many milliseconds
> you would need in a digital delay.
>
> A number of uC's have DRAM refresh circuitry that automatically does
> the refresh for
> you. I worked with a Coldfire chip that did.
>
> (* jcl *)
>
> --
>
> You can't create open hardware with closed EDA tools.
>
> http://www.luciani.org