Hi Bob,


> 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?

The FREEZ bit is set for all instructions sent to it by the ICD card, but
this is AFTER the register read/writes are performed.

This is a good question and somebody from Microchip should explain how the
code executes.

> 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?

Yes.

myke

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