1 megabit SRAM for SPI or parallel interface.

I saw a link to this while surfing for solutions to something different.

http://www.vlsi.fi/fileadmin/news/PressReleaseVS23S010.pdf

The VLSI Solution VS23S010 is an easy to use one megabit static RAM device. The memory can be accessed via a standard SPI compatible serial bus (1, 2 and 4-bit modes), or via an 8080-type 8-bit parallel bus similar to nand flash devices. One of the main applications for the VS23S010 is microcontroller RAM extension. Internet streaming applications, which are becoming increasingly popular, will benefit from the large buffer memory provided by VS23S010. For an example of usage, please see VLSI's internet streaming presentation at http://www.vlsi.fi/fileadmin/presentations/vlsi/Internet_streaming.pdf .

That's a pretty big bucket to not have the occasional holdups that SD will get.

They don't have them in the store and the request engineering samples gets 404'd. But the target quantity price is .99 Euros.

Hmmm, interesting chip. Now I’m trying to think of a use for it :slight_smile:


Rob

It could make a nice SPI buffer or even set of buffers. Suppose it could fit between MCU and SD?

How would it fit in between? Don't you need the MCU to control the SPI lines? So you're still stuck with one or the other.

Maybe if you had two microcontrollers and a dual port SRAM, or a large FIFO chip - one parts reads data and writes it to the memory, the other pulls it and writes it to the SD card.

Cypress carries dualport SRAMs, I didn't dig in to see if any have serial interfaces. If parallel, then you'd probably need a few shift registers/part to hold the address & data while writing, or to hold the address and then capture the data while reading.

Or a data server module with dedicated MCU, SD and RAM buffer that would always take in data and write to the SD when it's ready, keep pages buffered for quick re-access. Something like the DEC Rainbow drives? I only ever heard of those shortly though.

Every so often I see a project idea that got thwarted because of SD delays, but not even every month. Usually the solution is do it a different way or use bigger hardware.

As it is, I have 64k bit SPI SRAMs I haven't had more than a mess-with use yet. Got a couple 256k's but they're surface mount which for me they might as well be on the moon.

Someone (Microchip?) sells RAM battery backup chips (similar to the battery backup for RTCs).

With a battery backup the VS23S010 would make a nice SD card or EEPROM replacement.

Could also use FRAM chip, then no battery is needed. I should work on that FRAM shield I keep thinking about. Too bad the chips are pricey, ~$12 for 128K x 8 http://www.mouser.com/Semiconductors/Memory/_/N-488qu?Keyword=fram+memory&FS=True

CB: I hadn't thought of that. It's DRAM that sucks more power just staying on and refreshing, isn't it?

CR: Cool stuff! Give it 3 years and the price will be down, or are things moving faster now? At first when I saw the name Ferroelectric RAM I thought "New age core?". Too bad, not really.

You can get 64kx8 FRAMs for about $2.50-5.00, maybe that's the sweet spot price wise at present.


Rob

Those prices are too low Rob - 8kx8 might be that low, but 32Kx8, 64Kx8m 128Kx8 are all more.
You can find 2V16Kx8 for < $5, anything larger is more.
At mouser.com anyway.
Last time I checked, they had much better selection than Digikey too.

GoForSmoke: CB: I hadn't thought of that. It's DRAM that sucks more power just staying on and refreshing, isn't it?

I have no idea. It's been too long since I needed to know that stuff.

You're lucky enough to have ever -needed- to know. I hope the work was interesting!

GoForSmoke: I hope the work was interesting!

Warning: stack overflow imminent. :D

stack overflow imminent.

:)

DRAMs do need constant refreshing, but whether or not they use a lot more power because of it I don't know.

Bob, yes you're right, I missed the "kb" thought it was "kB".


Rob