1. Example 19 Measuring Pulse Widths Using Interrupts
Lecture L8.3

2. PIM_9DP256
Block Diagram
Timer module

3. Timer Pins
PT0 – PT7
Pins 9,10,11,12,
15,16,17,18

4. Timer Pins
PT0 – PT7
Pins 9,10,11,12,
15,16,17,18
PT1 = Pin 10

5. Interrupts on rising and falling edges
HI_time
LO_time
Interrupts on rising and falling edges

6. MC9S12DP256B Interrupt Vectors

7. // Example 19: Measuring Input Pulse Widths on Channel 1
#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"
// Timer channel 1 interrupt service routine
void interrupt 9 handler1(){
HILOtimes1(); // update HI-LO times on Ch 1 }

8. void main(void) {
int period1; // period of input pulse train on Ch 1
int HI_time1; // measured HI time of pulse train on Ch 1
int LO_time1; // measured LO time of pulse train on Ch 1
PLL_init(); // set system clock frequency to 24 MHz
lcd_init();
HILO1_init();
while(1) {
HI_time1 = get_HI_time1(); // read new HItime1
LO_time1 = get_LO_time1(); // read new LOtime1
set_lcd_addr(0x00);
write_int_lcd(HI_time1); // write HItime on row 1 of lcd
set_lcd_addr(0x40);
write_int_lcd(LO_time1); // write LOtime on row 2 of lcd
period1 = HI_time1 + LO_time1;
set_lcd_addr(0x14);
write_int_lcd(period1); // write period on row 3 of lcd
ms_delay(100); }