Mu Code for HC12 is given below :
USER_STACKTOP equ $0a00 ;just above RAM area PORTA equ $0000 ;Port A register PORTB equ $0001 ;Port B register PORTP equ $0056 ;Port P register DDRA equ $0002 ;Port A Data Direction Register DDRB equ $0003 ;Port B Data Direction Register DDRP equ $0057 ;Port P Data Direction Register INTCR equ $001e ;Interrupt Control Register COPCTL equ $0016 ;COP Control Register TIOS equ $0080 ;Timer Input Capture/Output Compare Select TSCR equ $0086 ;Timer System Control Register TCTL1 equ $0088 ;Timer Control Register 1 TMSK1 equ $008c ;Timer Interrupt Mask 1 TMSK2 equ $008d ;Timer Interrupt Mask 2 TCNT equ $0084 ;Timer Counter TC7 equ $009e ;Timer Input Capture/Output Compare Register 7 TFLG1 equ $008e ;Timer Interrupt Flag 1
org $0800 start clr COPCTL lds #USER_STACKTOP movb #$00,DDRA ;make Port A all inputs movb #$ff,DDRB ;make Port B all outputs movb #$00,DDRP ;make Port P all inputs movb #$00,PORTB ;clear Port B movb #$80,TIOS ;Set Timer 7 to output compare movb #$05,TMSK2 ;Prescalar = /32 = 250KHz clock movb #$40,TCTL1 ;Set Timer 7 output to toggle movb #$80,TMSK1 ;Enable interrupt for Timer 7 output compare
;Set up Timer counter to output at 50ms intervals ldd TCNT ;Load Timer Counter into D addd T7RATE ;Add T7RATE to D std TC7 ;Store D to TC7H movb #$80,TSCR ;Enables timers movb #$C0,INTCR ;enables IRQ interrupt
cli ;clear interrupt mask - enable interrupts
backgnd nop bra backgnd
Timer7IRQ: ldab TFLG1 ;just to read it ldab #$80 ;clear C7F in TFLG1 stab TFLG1 ldd TCNT ;get entire TCNT at time of ;external hi-to-low pulse staa PORTB ;display hi-order TCNT
ldd TCNT ;Load Timer Counter into D addd T7RATE ;Add T7RATE to D std TC7 ;Store D to TC7H
rti
IRQ_ISR: ldab INT_COUNT ;load data incb ;increment data stab INT_COUNT ;store data rti ;return from interrupt
org $0900 flags dc.b $ff INT_COUNT dc.b $00 ;Data element to increment in interrupt T7RATE dc.w $30D4 ;Rate of T7 Interrupts org $0b20 dc.w Timer7IRQ
org $0b32 dc.w IRQ_ISR
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