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'[PIC]: MPLAB + 17C756 + Read External Memory Crash'
2001\09\30@234331 by Andrew E. Kalman

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Hi All.

I've got a board working with the 17C756 in external microcontroller
mode. I've verified that it can read and write to external RAM just
fine with my emulator (PICMASTER). I've also verified that if I try
to write to an area that has no RAM, sure enough, when I read it
back, I get 0xFFFF.

But any attempt to read external memory (i.e. memory above 0x4000) in
MPLAB 5.20 (e.g. via the Modify Window, with Memory Area=Program and
"Read" button) results in MPLAB crashes. I've set the PICMASTER's
Configuration to "Extended Microcontroller" and the Memory to
"Off-Chip Memory ... from Target Board".

I know the new, non-0xFFF data is out in RAM, because I read it back
via a function and assign it to a local variable, which is watch in a
Watch Window. But I can't seem to see it directly, neither through
the Modify Window nor through the Program Mmeory Window.  If I use
the Modify window to _write_ to program memory (e.g. all 0's, a nop),
the Program Memory window shows the nop, but it seems to be "fake" in
that a read of the same location causes an MPLAB crash, etc.

All help and suggestions appreciated. The 17C756 circuit in question
is in Application Guide AG-5 on our website.

Thanks,
--

 ______________________________________
Andrew E. Kalman, Ph.D.


Salvo(TM), The RTOS that runs in tiny places(TM)
Pumpkin, Inc.
750 Naples Street
San Francisco, CA 94112
tel: (415) 584-6360
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'[PIC]: MPLAB + 17C756 + Read External Memory Crash'
2001\10\01@233256 by Douglas Wood
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There is a timing bug in the "regular" PICMASTER pod that causes problems
with table reads and writes. I had to move to the "CE" version of the pod.
That could be part of your problem.

Douglas Wood
Software Engineer
.....dbwoodKILLspamspam@spam@kc.rr.com

Home of the EPICIS Development System for the PIC and SX
http://epicis.piclist.com

{Original Message removed}

2001\10\02@112354 by Andrew E. Kalman

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Douglas Wood <dbwoodspamKILLspamKC.RR.COM> wrote:

>There is a timing bug in the "regular" PICMASTER pod that causes problems
>with table reads and writes. I had to move to the "CE" version of the pod.
>That could be part of your problem.


Thanks -- I had seen that mentioned.

Right now, the program works fine, reading and writing to external
RAM. If I compile with code in that external RAM, it shows up in the
Program Memory Window after a Build Project / F10.  But I can never
verify (by reading back) any _changes_ to the external RAM.

To me, it looks like MPLAB shadows the external RAM with its own buffer.

Oh well, the code is working right now, so I guess I'll live with it.

Regards,
--

 ______________________________________
  Andrew E. Kalman, Ph.D.   .....aekKILLspamspam.....pumpkininc.com

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