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'F87x In Cirquit Debugger resources'
1999\09\06@103647 by Morgan Olsson

picon face
Don«t you just hate undefined resource needs?

Reading in the F87x documentation 30292a.pdf, page 148, table 12-7, "DEBUGGER RESOURCES":
   "  Data memory:    TBD  "   (Heck!!  I thought at first)

Realizing it is dependant on the debugger firmware that will be downloaded (and therefor naturally not included in this hardware manual), i read in the MPLAB-ICD users guide as below so that is OK.

Also, the documentation of port B page 31 fig 3-4 is not updated to show debugger connections (Debugger use Port B 6:7).
According to page 134, fig 12-1, setting DEBUG=0 enables debugger (yes) and the pins are dedicated to the debugger.

Does this mean we can write anything we like in PORTB and TRISB 6:7 at any time?

According to page 31, Figure 3-4, any debugger activity will set RBIF (interrupt on change).  Hope there is some logic added to prevent having a RBIF interrupt after every singlestep, having activated the interrupt on change...
Can be tested, but having little spare time to test everything, thas is what documentation is for...

Reading further in the ICD manual:
The following I/O pins are not functioning correctly: RB3, RB6 or RB7.
These pins are reserved for programming/debugging. Refer to Section\  for more information.

But...  The ICD is not using RB3, I read somewhere else!  So by just cutting that useless connection we could use the ICD *and* use RB3 in our application.
(And we have to affix a pulldown resistor to RB3 and make sure no ecternal cirquit is pulling it high during reset or else the PIC will enter low voltage programming mode, am I right?)

More from the ICD maual:

Due to the built-in in-circuit debugging capability of the PIC16F87X and ICSP function offered by the Debugger, the MPLAB-ICD will use the following on- chip resources:

á     MCLR/VPP shared for programming
á     RB3 reserved for low-voltage programming

NOTE: MPLAB-ICD does not support low-voltage programming. Disable this function while using the ICD.

á     RB6 and RB7 reserved for programming and in-circuit debugging

                  ****RB3 not mentioned!***

á     Six (6) general purpose file registers reserved for debug monitor:
70h, 1EBh to 1EFh
                 <******* FILE REGISTERS *****

á     First program memory location (address 0x000) must be a NOP instruc tion
á     Program memory 0x1F00-0x1FFF reserved for Debug Code
á     One stack level not available

Hope this rambling have helped somebody, and maybe somebody can answer my questions.

PS  Anybody spotted a F87x document errata yet?  DS


Morgans Reglerteknik, HŠllekŒs, 277 35 KIVIK, SWEDEN
  tel +46(0)414-446620, fax -70331,

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