Microchip Technology MPLAB ICE, User Manual

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2001 Microchip Technology Inc. DS51159B-page 151
Debugging Techniques
The variable
num_out
is being written from within the
delay2
routine as a
result of the
decfsz delay_cnt
instruction. On closer inspection of the
delay_cnt
variable, you will find that it is being used as a 16-bit variable, but
in the source, it was only set as 8-bit. So, it overlaps with
num_out
, trashing it
in the delay routine.
Change the source code so that
delay_cnt
is set up as a 16-bit variable,
(i.e., change
delay_cnt
to
delay_cnt:2)
.
Figure A.13: Source Code File Update
A.4.3 Negative variable
When a particular variable gets to a signed negative value (8 bits), the
program misbehaves.
By using a sequential trigger and the trace display, you can see what is
happening when the variable goes negative.
To clear all break, trace and trigger points, select Debug>Clear All Points.
Configure the trace display (Window>Trace Memory, Options>Configure) to
focus on the source and destination address and data.