External SRAM recommendations?

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#1
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It seems like there are a lot of opinions about what SRAMs to use for external expansion for AVRs, though these are usually expressed generically ("the Samsung part," "the Winbond part"). I'm working on my first AVR design with external SRAM and would find specific part #s that people have used successfully very helpful. I imagine others would, too (perhaps this info could be posted somewhere else on AVR Freaks). I'm particularly interested in parts that can run with no wait states with an ATMega at 16 MHz. I'm prototyping with an ATMega8515 but will ultimately build with an ATMega128; my reading of the datasheets suggests they have the same external memory iterface performance specs. I've already discovered that an AHC latch (e.g. 74AHC573) is preferred (in fact, recommended by Atmel). Thanks loads for your help!

Karl

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I would also love he hear what the rest of you have to say as i've yet to build a project using external ram.

However i was able to find references to some part numbers in other messages that seem to indicate they were used (assuming they worked)

Cypress CY62128B-70
Samsung K6T1008C2C

and they seem to use 74AHC573 for the latch though a few references to the LS version (don't know)

for reference to where i found it:
https://www.avrfreaks.net/index.p...
https://www.avrfreaks.net/index.p...

hope it helps and looking forward to hearing from someone who has actually done it.

-john

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At 16Mhz the clock cycle is 62.5ns. Once you decide what specific latch chip and the latency then you can determine the speed of the SRAM. Typically AHC chips are around 7ns whcih means you can use a 55ns chip or faster without wait states. If you use wait states you can use chips up to 120ns.

Any SRAM chip with the appropriate voltage and that is 8 bits wide will probalby do. almost all support RD\ and WR\ singals and a CS\ .

do a search on digikey for SRAM and pick thos that have the voltage you want, that are 8 bits wide, that are of the size you wont (note that you canty get 64K or 60k byte SRAM so you will have to go to 128K x 8) and that has a 55ns speed or faster (refer to first paragrpah).

If you work 3V then any old mobile phone has at least one compatible SRAM chip in it. (If you dont mind SMD devices).

Lachlan