Cheap SRAM?

[Florian Student]

Hi comp.arch.fpga,

I know it's a bit off-topic but because I think that some of you might
be able to help me I'll ask anyway.

I'm planning to connect some ram to a cpld for fast data acquisition.
Probably using sram instead of dram should be easier because no refresh
signal is needed and it might also be faster(?)

Does anybody of you have a recommendation what device I should use; it
should have >= 1 MBit capacity and not be to expensive. Also, it should
be possible to order very low quantities of it.

Thank you in advance,
Florian

 

[Dave Garnett]

A good place to start is something like the DigiKey catalogue (because they
will happily sell you one of !). Cypress, for instance make a wide range of
async and sync srams - however, your choice may well be limited by the
package types available. Many devices now are only available in surface
mount and the high performance ones really need to be mounted on something
with proper ground and power planes.

If you are thinking faster than 80MHz, then Synchronous is the way to go (or
you could double buffer, or go narrow->wide in the cpld). The possibilities
are endless ...

If you went to something like a spartan IIe fpga, then you could use the
internal memory as part of the buffering strategy, and get a more flexible
architecture than you would with the cpld !!

enjoy !

Dave

"Florian Student" <studenfn@trick.informatik.uni-stuttgart.de> wrote in
message news:c73qvi$aju$1@inf2.informatik.uni-stuttgart.de...

Hi comp.arch.fpga,

I know it's a bit off-topic but because I think that some of you might
be able to help me I'll ask anyway.

I'm planning to connect some ram to a cpld for fast data acquisition.
Probably using sram instead of dram should be easier because no refresh
signal is needed and it might also be faster(?)

Does anybody of you have a recommendation what device I should use; it
should have >= 1 MBit capacity and not be to expensive. Also, it should
be possible to order very low quantities of it.

Thank you in advance,
Florian

 

[john jakson]

Florian Student <studenfn@trick.informatik.uni-stuttgart.de> wrote in message news:<c73qvi$aju$1@inf2.informatik.uni-stuttgart.de>...

Hi comp.arch.fpga,

I know it's a bit off-topic but because I think that some of you might
be able to help me I'll ask anyway.

I'm planning to connect some ram to a cpld for fast data acquisition.
Probably using sram instead of dram should be easier because no refresh
signal is needed and it might also be faster(?)

Does anybody of you have a recommendation what device I should use; it
should have >= 1 MBit capacity and not be to expensive. Also, it should
be possible to order very low quantities of it.

Thank you in advance,
Florian

I might suggest pseudo static ie DRAM< packaged as a SRAM with simple
IO ans hidden auo refresh. I believe they are used in cell phones that
means they should be very cheap & low power, but it might mean you
need to order large vol. Anyway some some samples might be available.
Can't remember the vendors, try Micron,Infineon,Samsung to start.

hope that helps, use google pseudo static dram
or something
regards

johnjakson_usa_com

 

[John_H]

I was finding the old Micron Synchronous SRAM parts to be priced best around
the 4Mbit size - the smaller die aren't so popular anymore. Micron sold
their line to Cypress so check them out.

There are different flavors of Synchronous SRAM, the least expensive
requiring a turnaround of 2 cycles on the data bus from a read to a write.
The good news is that these sub-$5 parts are good for up to 200MHz operation
in 100-pin TQFPs. The flavors include a single-clock result (flow-through)
or a two-clock result for the best performance (pipeline).


"Florian Student" <studenfn@trick.informatik.uni-stuttgart.de> wrote in
message news:c73qvi$aju$1@inf2.informatik.uni-stuttgart.de...

Hi comp.arch.fpga,

I know it's a bit off-topic but because I think that some of you might
be able to help me I'll ask anyway.

I'm planning to connect some ram to a cpld for fast data acquisition.
Probably using sram instead of dram should be easier because no refresh
signal is needed and it might also be faster(?)

Does anybody of you have a recommendation what device I should use; it
should have >= 1 MBit capacity and not be to expensive. Also, it should
be possible to order very low quantities of it.

Thank you in advance,
Florian