Bob Ammerman started this thread with:

> > > What is Mchip trying to say here? It looks to me that references to
> > > addresses 0x106 and 0x186 only affect the high two order bits of
> > PORTB/TRISB
> > > while references to 0x006 and 0x086 refer to the entire PORTB/TRISB.
> > Perhaps
> > > this is only true when in ICD code (INBUG == 1).
> > >
> > > What do you folks think?

Myke Predko noted:

> When I was doing the second edition of my PICmicro microcontroller book, I
> did some hacking of the ICD Interface and I found that in "ICD mode", all
> the hardware registers could be written to, but any changes to them didn't
> take effect until *after* a "return" instruction was executed.

Bob then wondered:

Would this still be the case if 'FREEZE' wasn't specified inthe debug
control register?

Myke continued on:

> While the PICmicro MCU was in ICD mode the only hardware resources that
> could be accessed correctly were:
> 1.  RB6/RB7 via 0x0106.  Only the Programming "Data" pin's TRIS bit could
be
> changed.  The Clock bit stayed in input mode.
> 2.  Program memory flash read/write controls.
> 3.  ICKBUG and BIGBUG (according to DS51242A - I didn't have this document
> when I was playing around with it so I called the registers "Reserve_E"
and
> "Reserve_F") could be read and written before executing a "return" to
return
> to the executing application.
> 4.  STATUS, PCLATH, FSR
> 5.  All File Registers
>
> If you are interested in seeing what I found, Take a look at pages 650 to
> 652 of the book.  On the CD-ROM, in the EMU-II directory, you will find
the
> source code that I created from the 256 instructions inserted into the ICD
> by the controller.

Finally, Bob queried:

I assume you mean the 256 instructions inserted into the device under test
by the ICD?

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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