Interrupt Yes or No - Difference

[savnik]

I have two codes which both of them works.
But i don't understand which is the difference with Interrupt and without Interrupt.
The operation both of them is the same

The first with Interrupt is :

'  On Interrupt - Interrupts in BASIC
'  Turn LED on-off.  Interrupt on PORTB.0 (INTE) turns LED1 on
'  Program waits 1 seconds and turns LED1 back off.


    ' 16F88

    led  var PORTA.2
    led1  var PORTA.3
    
    CMCON = 7
    ANSEL = 0

    On Interrupt goto myint    ' Define interrupt handler
    
    OPTION_REG = %00111111
    INTCON = %10010000         ' Enable INTE interrupt

loop:

    High LED
    Pause 100
    Low LED
    Pause 100
    Goto loop        ' Do it forever

    ' Interrupt handler
    
    Disable          ' No interrupts past this point
    
myint:

    High LED1        'If we get here, turn LED1 on
    Pause 1000       ' Wait 1 seconds
    Low LED1         ' If we get here, turn LED1 off
    INTCON.1=0       ' Clear interrupt flag
    Resume           ' Return to main program
    Enable

The second without Interrupt is :

    ' 16F88

    led  var PORTA.2
    led1  var PORTA.3
    
    CMCON = 7
    ANSEL = 0
    TRISB=%11111111
    
loop:

    if PORTB.0=0 THEN GOSUB myint 
    High LED
    Pause 100
    Low LED
    Pause 100
    Goto loop        'Do it forever
    
myint:

    High LED1        'If we get here, turn LED1 on
    Pause 1000       'Wait 1 seconds
    Low LED1         'If we get here, turn LED1 off
 
    RETURN

[HenrikOlsson]

Hi,
In this particular case the difference is that in the example using interrupts the latency is max ~100mS and in the example not using interrupts the latency can be up to 200mS.

In the first example PBP check if there is an interrupt pending between each PBP statement. Basicly:

Loop:
 Interrupt?
High LED
 Interrupt?
Pause 100
  Interrupt?
Low LED
 Interrupt?
Pause 100
 Interrupt?
Goto Loop

The second example checks the switch at the begining of each iteration thru the loop and since you have two Pause 100 in there it takes at least 200mS between each check. Depending on when you push the button the time it takes for program to respond will be between 0 and ~200mS.

/Henrik Olsson.