Page 260 - Making PIC Microcontroller Instruments and Controllers
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254 UIDERSIAIIDIIIG IHE COU TER+ COU TI G MARBLES
Il{TCOI{ |l{TEnACTTOI{
If you watch INTCON on the LCD while interrupts are set and cleared, you will notice
that the GIE (global interrupt enable) bir, birT of INTcoN, gers cleared auromarically
when an interrupt is set, and is reset automatically when you clear the interrupt flag
(if you had set it to 1 in the lirst place). This means that a second interupt cannot occur
before the first one that was set is cleared. Since PBP dllows the use of more than one
ON INTERRIJPT GOTO command in a program, strategies to make sure all intenupts
are handled prcperly can be formulated. It is best to do one interrupt at a time to keep
it simple while you ar€ a beginrcr
TmER2
The third timer is Timer2. This 8-bit timer canrot , e usel as a counter beca[se it does
not have the ability to respond to an extemal clock of any description- There is no line
on this timer intemal or exlemal) that we can connect an external signal to.
