Anyone found simple way to add 128k SRAM

Shael

I am working on a Propeller project and would like to add 128K sram 3.3v IC.·All the 3.3v sram seam to be in surface mount only. Has anyone found a simple way to add an sram to there Propeller Proto Board?

Mike Green

There are some 32 pin 512K x 8 SRAMs that come in DIP packages. They're about $6. If you have room for the chip, you could tie the extra address lines to Vss and just use 128K.

Look at the documentation for the TriBlade Prop (on this forum) for one example of their use. The part # for the SRAM is AS6C4008-55PCN.

virtuPIC

Serial or parallel interface? If SPI or I2C use one of the drivers in object exchange. If parallel, how many pins can you spend for your RAM? You might need some external latches / buffers

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Oldbitcollector (Jeff)

Mike Green said...
There are some 32 pin 512K x 8 SRAMs that come in DIP packages. They're about $6. If you have room for the chip, you could tie the extra address lines to Vss and just use 128K.

Mike,

Could you expand on this "tie the extra address lines to Vss and just use 128K"?
How many lines could we reduce this chip to under this configuration?

We need a "common standard" for an SRAM solution here just like that of Rokicki's SD driver.
I'm not sure SPI ram is the solution to the problem as speeds become an issue.

OBC

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jazzed

The simplest way is to put data on P[noparse][[/noparse]0..7] and address on P[noparse][[/noparse]8..24] use one of P26-P29 for WE and tie OE and CS to VSS. You can free up pins but have slower access if you use a 74LV374 to set some address bits from P[noparse][[/noparse]0..7]. Definitely use Mike's suggestion on hardware.

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--Steve


Propalyzer: Propeller PC Logic Analyzer
http://forums.parallax.com/showthread.php?p=788230

Shael

Hi Mike;

Thanks for the tip. Except for the 55ns speed should work fine.

Mike Green

OBC,
A 128K SRAM uses 17 address lines (A0..A16). A 512K SRAM uses 19 address lines (A0..A18). If you only want to use 128K out of 512K, then you can connect the last two address lines to Vss (A17 and A18) and save 2 Prop pins.

mynet43

A couple of other options someone might find useful:

Cypress makes a 2Mx8 45ns SRAM, CY62167EV30. Of course this requires 21 address lines.

In my case, I only need to read this sequentially, rather than randomly.

I have a really simple circuit that enables you to use all 21 address lines by using only a few control lines from the Propeller.

A couple of 74HC4040 counters are cascaded to increment the address lines on command from the Prop.

I've attached a partial schematic to show how it's done. Let me know if anyone would like more info.

My application allows a camera to store data in the SRAM, then reads it to analyze the image.

Jim

Ale

Get Cluso's tribladeprop plenty of room (SRAMs) and extra goodies