Do you have a keypad or buttons between Rd4:7 and Rb4:7 ?
You must enable pull-up resistor on Rb or to put aditional external
resistence to Vcc.
The folowing routine was written for jal but is almost in asm.
It reads the Rb7 -variable usa and Rb6 -variable apa
and detect low to high transition on this pins.
Check also the AN566
procedure interrupt_on_change is
pragma interrupt
assembler
local loop, usa_p, apa_p, out n
movwf w_temp -- save
swapf status, w
movwf status_temp
loop: bcf intcon_gie -- disable all interrupts
btfsc intcon_gie -- be sure
goto loop
btfss intcon_rbif -- test if interrupt
goto out -- if not go out from isr
btfsc usa -- if yes test which pin
goto usa_p
btfsc apa
goto apa_p
goto out
apa_p:
bcf intcon_rbie -- disable irq on change
bsf apa_flag
goto out
usa_p:
bcf intcon_rbie
bsf usa_flag
out:
bcf intcon_rbif -- else prepare for next interrupt
swapf status_temp, w -- restore
movwf status
swapf w_temp, f
swapf w_temp, w
retfie
end assembler
end procedure
On Fri, 12 Jan 2001, Andrew Quinn wrote:
{Quote hidden}> Port B Interrupt on change has really got me stumped. I have looked
> everywhere and can't find anything that explains why I can't get the
> following test code to work. I can only assume that the interrupt doesn't
> happen because RD3 is never set when I toggle any of the RD4:7 lines.
>
> If anyone can shed any light on this it would be most appreciated?
>
> Regards.... Andrew
>
> list p=16f877
>
> ; Include file, change directory if needed
>
> include "p16f877.inc"
>
> ORG 0x0000
>
> NOP
>
> CLRF STATUS
>
> CLRF PCLATH
>
> GOTO START
>
> ORG 0x0004
>
> BSF PORTD,3
>
> BTFSC PORTB,7
>
> GOTO $-1
>
> MOVF PORTB,W
>
> BCF INTCON,RBIF
>
> RETFIE
>
> START BSF STATUS,RP0
>
> BSF OPTION_REG,7
>
> MOVLW B'11110000'
>
> MOVWF TRISB
>
> MOVLW B'00000000'
>
> MOVWF TRISD
>
> MOVWF TRISE
>
> BCF STATUS,RP0
>
> CLRF PORTB
>
> CLRF PORTD
>
> BSF PORTD,2
>
> CLRF INTCON
>
> BSF INTCON,GIE
>
> BSF INTCON,INTE
>
> BSF INTCON,RBIE
>
> HERE GOTO HERE
>
> END
>
> --
>
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