May 18, 1992




USING THE DEBUG DIRECTIVE:


NOTE: This directive really stretches the limits of the Downloader hardware
      and may not always work.  However, when it does operate, it can be very
      useful.


If you have the PIC Downloader, there is a directive you can use to read back
register contents and I/O pins while your program runs.  This directive, called
"DEBUG", is inserted in your source file.  DEBUG has no parameters and may only
be inserted in your program once (if you need to monitor registers at various
points in your program, include the DEBUG directive in a subroutine which can
be called as necessary).

When DEBUG is encountered in your program, the Downloader will send register
contents (except 08h-0Fh) and I/O pins back to the PC.  The PC will display a
special screen for this data.  From the PC, you can press <SPACE> to halt your
program when it passes through DEBUG; pressing <SPACE> again allows your
program to continue running until it reaches DEBUG again.  To resume normal
operation, press <RETURN>.

The DEBUG directive does use some resources for its work, as shown below:

      1) 8 words at the point of insertion

      2) 69 words at the end of program memory

      3) Contents of registers 08h-0Fh are destroyed BEFORE being sent to the
         PC (the PC displays question marks for these registers).