>  A year ago, I used a 7x6 LCD for a simple RPM-counter. The 16C55
>  did drive the LCD directly and it worked but not very well. There
>  is an app-note for this: AN563.

Thanks for the recommendation and your thoughts Connie. I believe I have a
way of doing it using 11 tristate lines (for a 7X4 LCD) using 4 passes per
refresh cycle. The big issue is the effect of leakage current while PIC
lines are triatate (could be tricky at high tempertures).

I can image some of the difficulties with using a non-interrupt capable PIC
for this (16C55). Namely, keeping the timing symetrical to eliminate DC
bias. I tend to use the TMR0 interrupt as a foreground task to 'virtualize'
the hardware for the application code. This technique has been very
sucessful for me. I'm currently completing a design that uses a 220R
resistor pack, PIC16C622, and a 74HC374 latch to multiplex 4 8 segment
displays and 8 individual leds as an 8X5 LED array. Works great, foreground
loading is on the order of 10-20% or so, with a refresh rate of 100Hz. The
foreground runs also timers, and scans, debounces, and provides other
special functions (like auto-repeat) for 8 switches, etc.

I'll check into AN563 as well as the new LCD driver PICs.

Thanks again.

Regards, Dana Frank Raymond
dfr@icom.ca