The January 1997 issue of Electronics Now has a interesting article on
 using the PC printer port as a logic analyzer.  I have known this was
possible
for a long time.  However I never had the time or energy to write the PC
user interface software.  With the Electronics Now design the software is
already done and on their BBS.

I have not built the device yet, although I hope to in the next several
days.
Because they wanted universal compatibility, they only use the five
control
lines as inputs, so five lines can be sampled at once.  The time step in
the
article is not directly speced.  Rather it is mentioned that max
resolution will vary
based on the speed of the PC running the software.  The range given was
0.8uS to 7uS.   Obviously faster is better.  However for much of my
 microprocessor stuff, I can temporarily slow down the clock, so
 samples every 1uS would be very useful.  With such a device, I could
see the interrupt occur on one line, and then have four other lines to
monitor the PIC's response to the interrupt.  This design auto-calibrates
itself,
so that by scrolling forward in time, I can accurately judge how long it
took to
 service the interrupt,  how frequently they are arriving etc.

Does anyone have any experience with either this device or printer port
logic
analyzers in general?  With a bi-directional printer port and the right
PC
software eight traces of data would easily be possible.

If their is any interest in this topic, I will post my results to the
list.

 --- Steve