I think what Bruce is trying to find out is how to use the ICD in a
general way so that it can be added to any project. ie. what do you need
to know to design your own ICD function? (not just how do you use
d877.hex). There are hints in previous threads that it is not that
difficult to do but I cannot find an example of source code that shows how
to access the ICD function. If the inner workings of the ICD were known
you could then use this to create your own custom pic operating systems!.

Here is what I know (from snippets I have read on this list):
If the ICD has been enabled in the configuration fuses then the pic
hardware will check RB6 and RB7 for 0V, if RB6 and RB7 are at 0V then the
user program will run normally from the reset vector otherwise a different
vector will be picked up from 0x18F and 0x18E (I think) and will then run
code at that address. The ICD code can be anything you want from a full
blown ICD application (mplab style) to a simple function that looks for a
button press on a port bit and executes the next (user) instruction.  You
can see from this that the ICD is not rocket science and that anyone with
a bit of pic programming experience could write there own ICD routines!.

Can anyone fill in the details from the brief and incomplete description
above to enable us to get at the ICD?.

----- John

On Fri, 26 Jan 2001, James Newton wrote:
> It has been built several times and works perfectly with MPLAB
> How do people not find these FAQs?
> If you hit piclist.com and search for "BUILD AND ICD" you get right to it.
>

>
> Have any of you had success building your own ICD for the Pic16F87x that
> works with MPLAB (or even one that doesn't use MPLAB)?
>
> There is some info contained in the piclist archive, but nothing that shows
> a successful attempt at it, mostly bits and pieces or quotes from elsewhere.
>
> I did find the d877.hex disassembly - thank you very much:
> http://www.piclist.com/techref/microchip/16f877/xicd.htm
>
> And the MPLAB-ICD Module Schematics:
> http://www.microchip.com/Download/Tools/PICmicro/ICDS/MPLABICD/etn21d.pdf
>
> The early bits and pieces I found seemed to imply that this was a reasonable
> project. But it now appears much more reasonable to simply purchase
> Microchips package.
>
> Wondering what your experiences have been like.
> Bruce.

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