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; list p=16f871 ; list directive to define processor
#include <p16f871.inc> ; processor specific variable definitions
__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _XT_OSC & _WRT_ENABLE_ON & _LVP_OFF & _CPD_OFF
;__CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _EXTRC_CLKOUT
;**********************************************************************
M_SAVE_STATE macro
mov wf w_saved
movfw STATUS
movwf status_saved
endm
M_RESTORE_STATE macro
movfw status_saved
movwf STATUS
swapf w_saved,f
swapf w_saved,w
endm
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
count RES 1
count2 RES 1
ledA RES 1
ledC RES 1
ledB RES 1
;**********************************************************************
STARTUP CODE 0x000 ; 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 0x004 ; interrupt vector location
goto interrupt
;**********************************************************************
PROG1 CODE
interrupt
M_SAVE_STATE
M_SAVE_STATE ; try using twice a macro
; increment duty cycle
; btfss CCP1CON ^ BANK0,4
; goto duty_cycle_inc_bit0
; bcf CCP1CON ^ BANK0,4
; btfss CCP1CON ^ BANK0,5
; goto duty_cycle_inc_bit1
; bcf CCP1CON ^ BANK0,5
; incfsz CCPR1L ^ BANK0,f
; goto update_duty_cycle_done
;duty_cycle_inc_bit0
; bsf CCP1CON ^ BANK0,4
; goto update_duty_cycle_done
;duty_cycle_inc_bit1
; bsf CCP1CON ^ BANK0,5
;update_duty_cycle_done
; increment count
decfsz count,1
goto done
movlw .10
movwf count
; blink and output
movfw ledB
xorlw B'00001111'
movwf ledB
movwf PORTB
done
bcf INTCON,2 ; reset TMR0 interrupt flag
M_RESTORE_STATE
retfie ; return from interrupt
;**********************************************************************
start
; initialize microchip
clrf TMR0 ^ BANK0
clrf INTCON ^ BANK0
; clrf PORTA ^ BANK0
clrf PORTB ^ BANK0
; clrf PORTC ^ BANK0
; clrf PORTD ^ BANK0
; clrf PORTE ^ BANK0
banksel TRISA ; bank 1
; clrf TRISA ^ BANK1 ; all outputs
clrf TRISB ^ BANK1 ; all outputs
; clrf TRISC ^ BANK1 ; all outputs
; clrf TRISD ^ BANK1 ; all outputs
; clrf TRISE ^ BANK1 ; all outputs
movlw B'11010101' ; set prescaler to 64
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
; initialize PWM
; CLRF CCP1CON ^ BANK0 ; disable CCP module
; CLRF TMR2 ^ BANK0 ; clear Timer2 (also set the pre-scaler to 1)
; MOVLW .1
; MOVWF CCPR1L ^ BANK0 ; set duty cycle = (CCPR1L+1)/(PR2+1) [25% for (31+1)/(127+1)]
; banksel PR2 ; select bank 1
; MOVLW .255
; MOVWF PR2 ^ BANK1 ; set period = Fosc/4/pre-scaler/(PR2+1)
; BCF TRISC ^ BANK1,2 ; set CCP1 pin as output
; banksel PIR1 ; back to bank 0
; MOVLW B'001100'
; MOVWF CCP1CON ^ BANK0 ; set PWM mode (the 2 LSBs of the duty cycle are set to '00')
; BSF T2CON ^ BANK0,TMR2ON ; Timer2 starts to increment
; The CCP1 interrupt is disabled,
; do polling on the TMR2 Interrupt flag bit
;PWM_Period_Match
; BTFSS PIR1, TMR2IF
; GOTO PWM_Period_Match
; Update this PWM period and the following PWM Duty cycle
; BCF PIR1, TMR2IF
; initialize variables
movlw B00000101'
movwf ledB
movlw .10
movwf count
; loop forever
goto $
;**********************************************************************
END
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