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PICList Thread
'SIMM Memory and Pics'
1999\07\22@002014 by Brian Gracia

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Hello,

I have been following the thread on large storage needed for someones
project.  Could a SIMM module be hooked up (256K) to a pic.  I could
dedicate a pic to read/write to this module if necessary.

Has anyone ever done this?  Any web sites with articles/projects like this?

TIA,
Brian Gracia

1999\07\22@004405 by Thomas Brandon

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Microchip has an application note on attaching SRAM to a PIC16CXX (TB011).
This application note shows a circuit in which 2x256K(32Kx8) chips are
hooked up using a 16-bit address bus multiplexed with an 8-bit data bus
(total of 19 pins).

There is also an application note on connecting external memory to a
PIC17xxx via it's inbuilt bus (TB005).

The opnly limitation is the size of address bus you can manage. Obviously
you can get a very large bus with lots of multiplexing but this adds
components and complexity (both to circuit and to code). I'm also not sure
about whether timing would become an issue with more chips.

However, it is certainly possible to hook up at least 256K to almost any PIC
with an efficient use of pins.

Hope that helps,
Tom.
{Original Message removed}

1999\07\22@131235 by William K. Borsum

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At 02:44 PM 7/22/99 +1000, you wrote:
>Microchip has an application note on attaching SRAM to a PIC16CXX (TB011).
>This application note shows a circuit in which 2x256K(32Kx8) chips are
>hooked up using a 16-bit address bus multiplexed with an 8-bit data bus
>(total of 19 pins).
>
>There is also an application note on connecting external memory to a
>PIC17xxx via it's inbuilt bus (TB005).
>
>The opnly limitation is the size of address bus you can manage. Obviously
>you can get a very large bus with lots of multiplexing but this adds
>components and complexity (both to circuit and to code). I'm also not sure
>about whether timing would become an issue with more chips.
>
>However, it is certainly possible to hook up at least 256K to almost any PIC
>with an efficient use of pins.

I'm planning on using a serial latch to latch a starting count into a
counter, then pulse the counter to step through the addresses--which are
the parallel outputs of the counter--8, 16, 24, 32 or whatever address's
are needed.  simple, clean, and very efficient on PIC pins.  Suggest
standardizing of VLC parts as they will run on 3 or 5 volt power and accept
inputs to 7 volts.  Great logic family. and very low power.,

Enjoy
Kelly

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All legitimate attachments to this email will be clearly identified in the
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William K. Borsum, P.E.
OEM Dataloggers and Instrumentation Systems
<spam_OUTborsumTakeThisOuTspamdascor.com> & <http://www.dascor.com>

1999\07\22@180342 by Eric Oliver

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I have hooked a Dallas 2MB NVRAM to a 16C77 using cascaded 595's for the
address and an 8 bit data bus.  If I remember right, I used the extra
outputs on the 595's for the control lines on the NVRAM. Didn't test it
much but it worked.

Eric

On Wednesday, July 21, 1999 11:44 PM, Thomas Brandon
[SMTP:.....tomKILLspamspam@spam@PSY.UNSW.EDU.AU] wrote:
> Microchip has an application note on attaching SRAM to a PIC16CXX
(TB011).
> This application note shows a circuit in which 2x256K(32Kx8) chips are
> hooked up using a 16-bit address bus multiplexed with an 8-bit data bus
> (total of 19 pins).
>
> There is also an application note on connecting external memory to a
> PIC17xxx via it's inbuilt bus (TB005).
>
> The opnly limitation is the size of address bus you can manage. Obviously
> you can get a very large bus with lots of multiplexing but this adds
> components and complexity (both to circuit and to code). I'm also not
sure
> about whether timing would become an issue with more chips.
>
> However, it is certainly possible to hook up at least 256K to almost any
PIC
{Quote hidden}

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