> Thanks Bob,
> =

> I was hoping that was how it worked, but was starting to wonder.
> =

> It's funny, I feel like I have a reasonable understanding of how a Pic wo=
rks ...
>  but when I go to do something specific (that I haven't done before) ... =
all
> these other doubts pop up.
> =

> No substitute for experience I guess.
> =

> Anyway, at least my program should have some hope of running now that you =

> guys have sorted me out on my main concerns.
> =

> Thanks,   Roger

You can actually use the simulator that is included in MPLAB to singlestep =

through your code. This is a very useful learning experience. When in doubt=
, I =

usually go through the suspicious code with the simulator and with all poss=
ible =

variations in the input data to check that it always work as expected.

Even though I have used the PIC micros for more than 15 years now, I still =
find =

new ways of doing things. The last one was SUBLW 0, which does a one =

instruction 2-complement negation of w.

Here is a couple of other not so obvious examples of how things can be done =

differently and more efficiently on the midrange PIC, even though it only h=
as =

30-something instructions:

  btfss  reg,bit
  goto   end_test
  btfss  another_reg,another_bit =

  goto   end_test
do_work:

which can be rewritten as:

  btfsc  reg,bit
  btfss  another_reg,another_bit
  goto   end_test
do_work:

Yet another one:

  movlw  1
  xorwf  reg,w
  btfss  status,z
  goto   test_case_15
  ...    ;do work for case 1
  goto   end_work
test_case_15
  movlw  15
  xorwf  reg,w
  btfss  status,z
  goto   test_case_28
  ...    ;do work for case 15
  goto   end_work
test_case_28
  movlw  28
  xorwf  reg,w
  btfss  status,z
  goto   end_work
  ...    ;do work for case 28
end_work

which can be rewritten as:

  movf   reg,w
  xorlw  1
  btfss  status,z
  goto   test_case_15
  ...    ;do work for case 1
test_case_15
  xorlw  1^15
  btfss  status,z
  goto   test_case_28
  ...    ;do work for case 15
test_case_28
  xorlw  15^28
  btfss  status,z
  goto   end_work
  ...    ;do work for case 28
end_work

/Ruben


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

-- =

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