> about the "running" switch: the machine have a part that
> move alternately all the time (forward - backward) so each
> time the moving part is crossing the middle of it's travel it
> press a switch

OK, that's something that an external interrupt pin would be
useful for. When the switch is activated by this moving piece
of machinery it can alert the PIC a couple of ways.

One is to use the INT flag to store this event. Whether or not
the external interrupt is enabled, INTF will be set by a switch
transition until your code resets it. You could look for this flag
as part of the Timer1 ISR. If it's set, turn a LED on for a Timer1
interrupt period. An 80ms flash is quite noticeable, but you
could keep the LED on for the duration of a counter driven by
Timer1 IRQs

#define led porta,2

ISR
-----

bcf    led                                ;turn LED off by default
btfss  intcon,intf                    ;test for external event
goto  process_timer1_irq   ;no, carry on with no LED lit

bcf    intcon,intf                     ;yes, clear flag
bsf led                                   ;light LED

bcf    tmr1if                           ;clear Timer1 flag
process_timer1_irq            ;continue

retfie

The other way would be to have Timer0 as a counter and set it
to 0xFF. A pulse coming into RA4 will cause Timer0 to rollover
to 0x00 and set T0IF, which you can check for

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