1. Example 14 Real-time Interrupts
Lecture L6.1

2. Register Stacking for Interrupts

3. MC9S12DP256B Interrupt Vectors

6. void interrupt 7 handler(){ << you C code goes here >> }
Writing interrupt service routines in C and setting the interrupt vector
Vector number for real-time interrupt
void interrupt 7 handler(){
<< you C code goes here >> }

7. Real-Time Interrupt Registers
$0037

8. $0038

9. Real-time Interrupts
$003B

11. ; Real-time interrupt
; RTI_init();
RTI_init:
sei ;disable interrupts
ldaa #$59
staa RTICTL ;set rti to ms
ldaa #$80
staa CRGINT ;enable rti
cli ;enable interrupts
rts
; clear_RTI_flag();
clear_RTI_flag:
ldaa #$80
staa CRGFLG ;clear rti flag
rts

12. // Example 14: Real-time interrupt
#include <hidef.h> /* common defines and macros */
#include <mc9s12dp256.h> /* derivative information */
#include "main_asm.h" /* interface to the assembly module */
#pragma LINK_INFO DERIVATIVE "mc9s12dp256b"
void half_sec_delay(void);
unsigned short ticks, ticks0; // RTI interrupt counts
// RTI Interrupt Service Routine
void interrupt 7 handler(){
ticks++;
clear_RTI_flag(); }

13. void main(void) {
PLL_init(); // set system clock frequency to 24 MHz
seg7_enable();
RTI_init();
while(1) {
seg7dec(8); // display 8 on 7seg display
half_sec_delay();
seg7_off(); // turn off 7seg display }
void half_sec_delay(void){ // delay for 0.5 seconds
ticks0 = ticks;
while((ticks-ticks0)<49) {