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; list p=16f877
#include <p16f871.inc>
#include <test.inc>
__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _RC_OSC & _WRT_ENABLE_ON & _LVP_ON & _CPD_OFF
;**********************************************************************
BANK0 = 0x0
BANK1 = 0x80
BANK2 = 0x100
BANK3 = 0x180
;**********************************************************************
INT_VAR UDATA_SHR
w_saved RES 1 ; variable used for context saving
status_saved RES 1 ; variable used for context saving
TEMP_VAR UDATA_SHR 0x20
index RES 1
;**********************************************************************
STARTUP CODE ; processor reset vector
nop ; for debugger
movlw high start ; load upper byte of 'start' label
movwf PCLATH ; initialize PCLATH
goto start ; go to beginning of program
;**********************************************************************
INT_VECTOR CODE 0x0004 ; interrupt vector location
movwf w_saved
movfw STATUS
movwf status_saved
bcf INTCON,2 ; reset TMR0 interrupt flag
bsf PORTB,0
movfw status_saved
movwf STATUS
swapf w_saved,f
swapf w_saved,w
retfie ; return from interrupt
;**********************************************************************
MAIN CODE
start
; initialize microchip
clrf TMR0 ^ BANK0
clrf INTCON ^ BANK0
banksel TRISA ; bank 1
movlw B'11010100' ; set prescaler at 32 (32768 Hz / 4 / 256 / 32 = 1 Hz)
movwf OPTION_REG ^ BANK1 ; and start TMR0 (internal source clock)
movlw B'00000110' ; set PORTA and PORTE to be all digital
movwf ADCON1 ^ BANK1
banksel INTCON ; back to bank 0
bsf INTCON,T0IE ; enable TMR0 interrupt
bsf INTCON,GIE ; enable all interrupts
nop
END ; directive 'end of program'
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