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54 lines
1.9 KiB
54 lines
1.9 KiB
15 years ago
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list p=16f877
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#include <p16f877.inc>
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__CONFIG _CP_ALL & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _RC_OSC & _WRT_ENABLE_ON & _LVP_ON & _CPD_OFF
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;**********************************************************************
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BANK0 = 0x0
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BANK1 = 0x80
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BANK2 = 0x100
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BANK3 = 0x180
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;**********************************************************************
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w_saved EQU 0x70 ; variable used for context saving
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status_saved EQU 0x71 ; variable used for context saving
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index EQU 0x20
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;**********************************************************************
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ORG 0x000 ; processor reset vector
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movlw high start ; load upper byte of 'start' label
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movwf PCLATH ; initialize PCLATH
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goto start ; go to beginning of program
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;**********************************************************************
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ORG 0x004 ; interrupt vector location
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movwf w_saved
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movfw STATUS
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movwf status_saved
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bcf INTCON,2 ; reset TMR0 interrupt flag
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movfw status_saved
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movwf STATUS
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swapf w_saved,f
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swapf w_saved,w
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retfie ; return from interrupt
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;**********************************************************************
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start
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; initialize microchip
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clrf TMR0 ^ BANK0
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clrf INTCON ^ BANK0
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banksel TRISA ; bank 1
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movlw B'11010100' ; set prescaler at 32 (32768 Hz / 4 / 256 / 32 = 1 Hz)
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movwf OPTION_REG ^ BANK1 ; and start TMR0 (internal source clock)
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movlw B'00000110' ; set PORTA and PORTE to be all digital
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movwf ADCON1 ^ BANK1
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banksel INTCON ; back to bank 0
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bsf INTCON,T0IE ; enable TMR0 interrupt
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bsf INTCON,GIE ; enable all interrupts
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; loop forever
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goto $
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END ; directive 'end of program'
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