Memory module with Asynchronous R/W

Are there any memory IC's with a clock of at least 10Mhz, preferably more, that allows for async reading and writing? I need to be able to dump the memory serially, 1 bit at a time, in a continuous somewhat uninterrupted fashion while separately making random updates to the memory. I need max 1k of memory but I think I can even get away with

64 bytes.

Here the writing is not suppose to effect the timing of the reading. The application is to feed a cascaded collection of IC's serially as fast as possible where the memory acts as a lookup table. The table will need to be modified though and I would like to avoid stopping the reading just to write. The writing can be delayed somewhat as it's not critical.

I can, of course, use a much faster uC but even here the data rate will not be continuous as it will have to pause for making updates to the memory. Using DMA would help as I could update while the DMA is sending the bits down the stream. This of course is much more complex than having a simple ic that will do all this and do it better.

Reply to
James Rollins
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On a sunny day (Wed, 3 Jun 2009 14:53:24 -0700 (PDT)) it happened James Rollins wrote in :

8 x a 8 bits parallel in, serial out, shift register? Do those exist in HC7400?
Reply to
Jan Panteltje

On a sunny day (Wed, 03 Jun 2009 22:44:37 GMT) it happened Jan Panteltje wrote in :

Oh, error, you need 64 Bytes... FPGA perhaps with block RAM.

Reply to
Jan Panteltje

IDT or Cypress dual-port sram?

Something like IDT7133SA90J maybe. It's 2K x 16 bits.

John

Reply to
John Larkin

Sounds like you're looking for a dual-port RAM.

A quick search on

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turns up "about 71,800" hits. :-)

Have Fun! Rich

Reply to
Rich Grise

What is the serial data rate what is the write cycle time.

Bob

Reply to
<castlebravo242

I think Jan has your answer. A small FPGA would do this easily.

FPGAs are quite good at multi-port RAMs and ROMs. They're dead simple to build with the XIlinx tools (haven't used Altera or Actel yet - soon maybe).

At the speed above you could have dozens of asynchronous ports. ;-)

Reply to
krw

Farnell stocks a bunch of GSI's asynchronous SRAM. The GS71108AGP-10 offers 10nsec access time, which is fast enough to let you do four accesses in 100nsec (I've managed that with 12nsec SRAM). 128k x 8 seems to be a bit bigger than you want, but they aren't expensive (at around $5 each in small quantities).

Farnell also stocks some of GSI's synchronous-burst SRAMs which are rather faster, and not all that much more expensive. I've not used them, but they look as if they might be worth a look.

Reply to
bill.sloman

I'm unfamiliar with FPGA's. I've read up on the basics and it seems easy enough but. Although it seems rather pricey to get started(200+) and the ic's can seem expensive. I haven't seen an xlinix in low quantities under 50$.

From what I've read, CPLD would be better for the "bit banging" I have to do. Are these devices relatively equivalent in software and harder as far as programming? That is, is most of the difference "under the hood" and won't be a show stopper if I randomly choose one?

The fgpa seem rather convenient to use yet expensive and seem to require a lot of work testing. Of course the generality of such devices probably overcome such issues.

The dual-port ram does not seem to be what I'm after unless there there are serial versions as all I have seen are parallel. I also sorta need the output to sequential rather than random. Essentially what I'm looking for is a large serial register that can be programming like RAM. In fact a large serial register would work except that it would interrupt the output every time it needs to be programmed. I'm imagining this would be rather easy to accomplish with an fgpa with memory.

What would be some cheap user friendly fgpa's to get started with? I see some very cheap lattice cpld's for around 2$ and some actel and lattice fpga's for 5$ to 10$.

Reply to
James Rollins

I'm unfamiliar with FPGA's. I've read up on the basics and it seems easy enough but. Although it seems rather pricey to get started(200+) and the ic's can seem expensive. I haven't seen an xlinix in low quantities under 50$.

From what I've read, CPLD would be better for the "bit banging" I have to do. Are these devices relatively equivalent in software and harder as far as programming? That is, is most of the difference "under the hood" and won't be a show stopper if I randomly choose one?

The fgpa seem rather convenient to use yet expensive and seem to require a lot of work testing. Of course the generality of such devices probably overcome such issues.

The dual-port ram does not seem to be what I'm after unless there there are serial versions as all I have seen are parallel. I also sorta need the output to sequential rather than random. Essentially what I'm looking for is a large serial register that can be programming like RAM. In fact a large serial register would work except that it would interrupt the output every time it needs to be programmed. I'm imagining this would be rather easy to accomplish with an fgpa with memory.

What would be some cheap user friendly fgpa's to get started with? I see some very cheap lattice cpld's for around 2$ and some actel and lattice fpga's for 5$ to 10$.

Display controller?

Address and data latch for writing. Counter and shift register for reading. do not allow the write during the data output cycle allow it during the other seven intervals.

Bob

Reply to
<castlebravo242

e

The development tools are free and the small chips can be had for $5 or so. You don't need much.

CPLDs won't have the blockrams or distributed RAMs to build the dual- port structures from. You can do it with logic, but the dual-port RAM structures have everything you need already done.

Small ones aren't expensive at all. They really aren't any work testing, though bringup is a little more complicated. There is a rather steep learning curve. ...but it's worth it. ;-)

Dual-port gets you separate read and write ports that won't step on each other. How you access the memory is a another issue. You want serial, do serial.

That's about the right price range. To make things simple, I think you're going to want the RAM structures that FPGAs offer. I'm most familiar with Xilinx, but Actel or Altera should work too. Actel has the advantage of being flash based (which is why I'll likely go there for my next design). Actel also uses Synplicity for their *free* tools.

Reply to
keithw86

Start here:

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Google for other sites for beginners.

don

Reply to
don

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