LIST p=16F628 ;tell assembler what chip we are using
include "P16F628.inc" ;include the defaults for the chip
ERRORLEVEL 0, -302 ;suppress bank selection messages
__config 0x3D18 ;sets the configuration settings (oscillator type etc.)
cblock 0x20 ;start of general purpose registers
FLAG_REG
endc
CLRF FLAG_REG ;Init flag register
clrf FLAG_REG
CLRF PORTA ;Init PORTA
MOVF CMCON,W ;Load comparator bits
ANDLW 0xC0 ;Mask comparator bits
IORWF FLAG_REG,F ;Store bits in flag register
MOVLW 0x04 ;Init comparator mode
MOVWF CMCON ;CM<2:0> = 011
BSF STATUS,RP0 ;Select Bank1
MOVLW 0x07 ;Initialize data direction
MOVWF TRISA ;Set RA<2:0> as inputs
;RA<4:3> as outputs
;TRISA<7:5> always read ‘0’
BCF STATUS,RP0 ;Select Bank 0
CALL DELAY10 ;10µs delay
MOVF CMCON,F ;Read CMCON to end change condition
BCF PIR1,CMIF ;Clear pending interrupts
BSF STATUS,RP0 ;Select Bank 1
BSF PIE1,CMIE ;Enable comparator interrupts
BCF STATUS,RP0 ;Select Bank 0
BSF INTCON,PEIE ;Enable peripheral interrupts
BSF INTCON,GIE ;Global interrupt enable
DELAY10
nop
end