Hi KPL:

The idea is that when the prescaler is used with Timer 0 (this is an 8 bit 
timer/counter) the count frequency can be as high as 50 MHz (there are 
requirements about the prescaler setting).  This works with most PICs on TMR0. 
  It does not work on Timer 1 (the 16 bit timer/counter).  The PIC spec is in 
terms of time not frequency so it's easy to miss.

The problem is that there's no internal provision to read the contents of the 
prescaler.  In AN-592 Microchip describes how count the number of pulses from 
another pin that are needed to get the TMR0 prescaler to rollover.  This way 
you can read the prescaler value.

This is the method used on the numerous 50 MHz PIC counters that you can find 
on line.

The best info on driving the standard 44780 type LCDs is in the PICKit 2 
documentation.  Notice that they do it on a pin by pin basis, not using the 
more common nibble (half byte) basis.  This gives you the freedom of assigning 
pins first to get the needed features then using what's left over for the LCD 
instead of forcing you to use a hi or lo nibble.  This also makes for fewer 
problems.

But please ditch the obsolete 16F84() and use a 16F88 or one of the other more 
modern PICs.  See:
http://www.pacificsites.com/~brooke/PIC16F88.shtml

Have Fun,

Brooke Clarke
-- 
http://www.PRC68.com
http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

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