16F1823 - Can't get RA3 (MCLR) to be a switch input (attached switch resets PIC).

[HankMcSpank]

Now I'm sure this is simple - but I've stared at it to the point where I now need to go for a shave, but I need to use PortA.3 (which can be a MCLR pin), as an 'input' for a tactile switch...I want to use an internal weak pullup on that pin too.

What I'm getting Is the PIC resetting everytime I press the switch attached to pin 4 (PortA.3)....so it looks like MCLR is not being disabled. I've checked the associated .inc file in my PC's MPASM directory for the necessary syntax - i think i've got it right.

I've slimmed my program down to the basics...just to get to the bottom of this. A simple loop, when either one of two switches are pressed, A DT interrupt happens & I get some syntax on screen - but it aint right, Sw1 doesn't interrupt at all, Sw2 does, but I just see "Interrupt Sw1" on my screen
...and it doesn't exit until I press Sw1 (which threw me, but then I put a litte trap at the top of my program & established that Sw1 was simply resetting the PIC)

Top tips warmly received.....

@ __CONFIG _CONFIG1, _FCMEN_OFF & _FOSC_INTOSC & _WDTE_OFF & _MCLRE_OFF & _CP_OFF & _IESO_OFF & _BOREN_OFF & _PWRTE_OFF

DEFINE  OSC 4
INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System  PO90OOO9
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

RCSTA = $90   ' Enable serial port & continuous receive
TXSTA = $24   ' Enable transmit, BRGH = 1
SPBRG = 8     ' 115200 Baud @ 4MHz, -3.55%
SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator

'-------------------------------------------------------------------------

Osccon = %01101010     'sets the internal oscillator 

APFCON.2 = 0            ;Hserout onto RC.4 Pin 6
ADCON0 = 0
ADCON1 = 0

CM1CON0 = 0   ' COMPARATORS OFF
CM2CON0 = 0   ' COMPARATORS OFF

ANSELA     = %00010000  
ANSELC     = %00000100  
TRISA      = %11111111
TRISC      = %00000100  
OPTION_REG.7 = 0

WPUA  = %00101000
IOCAN = %00101000 

SW1    VAR PORTA.3
SW2    VAR PORTA.5
hserout ["reset", 13, 10]

ASM
INT_LIST  macro ; IntSource,    Label,         Type, ResetFlag?
    INT_Handler  IOC_INT,  _Switch_Interrupt,  PBP,  YES 
    endm
    INT_CREATE       ; Creates the interrupt processor
ENDASM
       
IOCAF = 0

@ INT_ENABLE IOC_INT   ; Enable 'Int On Change' interrupts


Loop1:
    hserout ["Waiting", 13, 10]
    pause 500
    GOTO Loop1
    'ENDIF


'+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Switch_Interrupt:
@ INT_DISABLE IOC_INT  ; Disable further IOC interrupts

        pause 10
        IF sw1 = 0 THEN
        HSEROUT ["INTERRUPT Sw1", 13, 10]
        goto interrupt_end
        endif
        
        IF sw2 = 0 THEN
        HSEROUT ["INTERRUPT Sw2", 13, 10]
        goto interrupt_end
        endif

interrupt_end:     
@ INT_ENABLE IOC_INT
@ INT_RETURN 


end