Harry,

I don't see where you clear the interrupt flag before leaving the
interrupt service routine.
If the interrupt flag is not cleared, and the PIC is going back into the
ISR right after it 
leaves the ISR, you'll get a loop that clears the ports, sets the LED's
on, leaves the ISR,
reenters the ISR, and then does it all again.  This happens so fast that
you can see the LED's
come on.

Just an observation.  However, I haven't worked with the 685 before, so
it may not behave the 
saame as the ones I have used.



	
Regards,

	
Jim


 

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of Harry H. Arends
Sent: Friday, August 29, 2008 3:28 PM
To: 'Microcontroller discussion list - Public.'
Subject: [PIC] No reaction using chanhe on interrupt

This is a second try to get the 16F685 working to respond on a signal
change on RB7.
I wrote this small piece of code on advise earlier after the first
question about this.
 
When i set a signal on RB7 niether RA0 or RA1 or both wil come on. Thit
i missed something in the datasheet on this matter. As far i can see i
have set all the registers correct.
 
;        errorlevel      -302, -305  ; Suppress Bank Warnings
            list        p=16F685, r=hex
            INCLUDE     "P16F685.INC"
            __CONFIG    0x3CE2
; --- Definetions section
----------------------------------------------------
; --- Macros definitions

; --- Constant values
#define     DCCIN   PORTB, 7        ; DCC signal input
 
; --- Variables in RAM
    cblock  0x070                   ; On bottom of all banks
INT_W                               ; Interrupt context registers
INT_STAT                            ;
EEDATA0                             ; EEPROM shadow variables
    endc
 
; --- Program section
--------------------------------------------------------
    org 0x000
PowerUp:
    clrf    STATUS                  ; Bank0 is default
    clrf    INTCON                  ; Disable all interrupts at first
    clrf    PCLATH                  ; All tables on Bank0
                                    ; Following the datasheet the above
could
                                    ; onmitted but we use it to be sure
    goto    Init
; --- Interrupt routine
------------------------------------------------------
    org 0x004
Interrupt:
    movwf      INT_W                   ; Save content register
1
    swapf       STATUS, W               ;
2
    movwf      INT_STAT                ;
3
    clrf          STATUS                  ; Interrupt uses BANK0
4
 
    btfsc        DCCIN                   ; DCC signal present
5
    
    bsf           PORTA, 0
    bsf           PORTA, 1
    nop
 
EndInt:
    swapf       INT_STAT, W             ; Restore content registers
49
34
    movwf      STATUS                  ;
50
35
    swapf      INT_W, f                ;
51
36
    swapf      INT_W, w                ;
52
37
    retfie                          ;                              53 54
38
39
; --- Set used registers in correct setting
----------------------------------
Init:
                                    ; These registers are in BANK0
    clrf         PORTA
    clrf         PORTB
    clrf         PORTC
 
    BANKSEL TRISA                   ; These registers are in BANK1
    clrf        TRISA                   ; Set to all outputs
    movlw   b'10110000'             ; Set RB7, RB5 and RB4 to Input
    movwf   TRISB
    clrf        TRISC                   ; Set to all outputs
    movlw   b'10001000'              ; Set Optionregister  to no
PullUps,
                                              ; no prescaller and WDT
1:1
    movwf   OPTION_REG
    clrf       WPUA                    ; Dont use WeakPullUp on PORTA
                                              ; We dont use IOC on PORTA
so leave it as  it is
 
    BANKSEL ANSEL                   ; These registers are in BANK2
    clrf         ANSEL                   ; Set to all digital I/O
    clrf        ANSELH
    clrf        WPUB                    ; Dont use WeakPullUps on PORTB
    movlw   b'10000000'             ; Set RB7 to InterruptOnChange PORTB
    movwf   WPUB
 
    BANKSEL 0x00                    ; Return to BANK0
    movlw   b'00110001'             ; Set Timer1 on at 1:8
    movwf   T1CON
    movlw   b'10001000'             ; Enable all unmasked interrupts and
                                             ; enable PORTA/PORTB
interrupt on change
    movwf   INTCON
 
    nop
    bsf     PORTC, 2
    nop
    goto    $
    end
 
Regards
 
Harry
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