Help with simplified SDRAM access


I'm building a very low cost PC Oscilloscope. I have lots of spare PC-100 SDRAM chips and would like to use them instead of buying FIFO. I cannot use the computers memory via PCI because the PCI card cannot guarantee memory access all the time. Therefore I would like to use SDRAM in my circuit board.

I understand it's complex to use SDRAMS. I have an idea that could simplify the job. Instead of having my circuit do all the initializations, etc. to the SDRAM, why not do it through software on the PC? Is this a good idea? I have no idea since I am not familiar with SDRAM. The software could have access to the pins of the SDRAM.

Does anyone have any suggestions, web sites, information? I have no idea what signals I would need to send to the SDRAM. Also, once the SDRAM is setup / initialized, how can my circuit save & read data to and from the SDRAM?

Many thanks!

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So, get familiar.

Google for datasheets on SDRAM chips. You can't generally throw more than a few dozen bytes at the SDRAM before doing something.

Reply to
Ian Stirling

If you're going through the PC, why not just poke the samples into the PC's memory?


Reply to
John Larkin

For the same reason you couldn't use the PC's own memory in the first place: accesses through PCI bus to the SDRAM chips' pins will rather likely be too slow to function correctly.

I don't think it's feasible for a one-off hobby project to implement your own SDRAM controller logic.

Hans-Bernhard Broeker (
Even if all the snow were burnt, ashes would remain.
Reply to
Hans-Bernhard Broeker

You can get a cheap FPGA evaluation board with SDRAM, and use an open source SDRAM controller core inside FPGA. You can get an open source PCI target core for the FPGA as well.

This reduces the PC Oscilloscope to basically three chips: FPGA, SDRAM and ADC.

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Regards, Allan

Reply to
Allan Herriman

Ok, you build your own board and adding the SDRAMS on it?

Yes, CPU/microcontroller can do that via a glue logic, which people call SDRAM controller, and that is the way it's suppose to be.

Do google for 'sdram controller', or go to sdram manf. and download a datasheet and digest it, good luck

Reply to

You're suggesting to use the computers memory via the PCI slot, correct? I would need to tie up the bus for several minutes. I was told the system bus will not allow that for very good reasons.

I am not sure what you are referring to as being too slow. I would only use the computer software to initialize the SDRAM, not for reading and writing purposes. My circuit would do the high speed reading and writing once the computer software initialized the SDRAM.

Reply to

SDRAM must be refreshed very often. An SDRAM controller handles both initializing and refershing the RAM. You can't do this over a PCI bus, so you'll need an SDRAM controller one way or another.

In case this isn't clear: the host PC cannot control PCI SDRAM chips quickly enough to make them happy. It is quite apparent that you don't know what SDRAM is or how it works. Go to

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and do some learning, and you should understand what everyone is saying a little better.



Reply to
Buddy Smith

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