Help with simplified SDRAM access

[yo]

Hi,

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!

 

[Ian Stirling]

Hi,

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 No.
with SDRAM. The software could have access to the pins of the SDRAM.

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.

 

[John Larkin]

Hi,

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!

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

John

 

[Hans-Bernhard Broeker]

[F'up2 cut down to one group --- should have been done by OP!]

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?

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.

 

[Allan Herriman]

[F'up2 cut down to one group --- should have been done by OP!]

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?

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.

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.

http://www.fpga-faq.com/FPGA_Boards.shtml

Regards,
Allan

 

[Marlboro]

Hi,

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.

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

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.

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.

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!

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

 

[yo]

[F'up2 cut down to one group --- should have been done by OP!]

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?

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.

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.

 

[Buddy Smith]

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.

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

ttyl,

--buddy