First try at DT_INT's, I failed! help please!

Old dogs can learn new tricks, it just takes a little more effort. Can someone please tell me why the RB0 interrupt only works once on this simple routine? This is my first attempt at DT_INT’s. Once I got MPASM set up on MCSP I thought it would be easy. I’m using X1 board with 16F877A and pulsing RB0 with a wire lead. It runs the leds once then will not run again. I’ve tried everything I can think of with no success.

Code:

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define osc 20
    option_reg.6=1 'rising pulse
    wsave  var byte $70  system
    wsave1  var byte $A0  system
    wsave2  var byte $120 system
    wsave3  var byte $1A0 system
    i      var byte
    LEDS    Var PORTD  ' Alias PORTD to LEDS
    TRISD = %00000000      ' Set PORTD to all output
INCLUDE "DT_INTS-14.bas"    ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"    ; Include if using PBP interrupts
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,  PBP,  yes
    endm
    INT_CREATE              ; Creates the interrupt processor
ENDASM
@  INT_ENABLE  INT_INT    ; enable external (INT) interrupts
Main:
  PAUSE 1
  PortD=0
  GOTO Main
'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:  LEDS = 1        ' First LED on
        Pause 500      ' Delay for .5 seconds
        For i = 1 To 7  ' Go through For..Next loop 7 times
                LEDS = LEDS << 1        ' Shift on LED one to left
                Pause 500      ' Delay for .5 seconds
        Next i     
@ INT_RETURN
      end

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OK, I have found out that it is returning from the interrupt. However I can not interrupt again for about ten seconds or the interrupt fails. A failure to interrupt forces another ten second delay before I can trigger again. Is there anything I can do to speed this process? On compile the program shows only 255 words long. I don’t understand this time delay before I can re enter the interrupt. Comments please…

Quote:

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I’m using X1 board with 16F877A and pulsing RB0 with a wire lead.

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That's the problem.

If you are using a wire to +5V, there's nothing to pull it back down.
The pin will hold a charge, and will slowly drain off, allowing it to re-trigger after a few seconds.

If you add a pull-down resistor it should work better.

Or, you can turn on PORTB pull-ups (OPTION_REG.7 = 0), make PORTB.4 LOW so you can use SW1 pushbutton.
Changing to OPTION_REG.6 = 0 will make it trigger on the falling edge (button press) instead of the rising edge (button release).

Thanks Darrel, I'll give it a try!

Yep! works great!

Quote:

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Originally Posted by Darrel Taylor

...
Or, you can turn on PORTB pull-ups (OPTION_REG.7 = 0), make PORTB.4 LOW so you can use SW1 pushbutton.
Changing to OPTION_REG.6 = 0 will make it trigger on the falling edge (button press) instead of the rising edge (button release).

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This is funny, I did this very exercise yesterday and posted it in the Code Examples. LOL

Robert
:)