Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual page 935

/* start timers */
r7.l = TIMEN5 | TIMEN4 ;
w[p5 + TIMER_ENABLE - TIMER_ENABLE] = r7;
/* write values for second period */
[p5 + TIMER4_PERIOD - TIMER_ENABLE] = r3;
[p5 + TIMER5_WIDTH - TIMER_ENABLE] = r2;
/* r0 functions as signal period counter */
r0.h = hi(N * 2 - 1);
r0.l = lo(N * 2 - 1);
(r7:1, p5:5) = [sp++];
rts;
timer45_toggle_hi.end:
isr_timer5:
[--sp] = astat;
[--sp] = (r7:5, p5:5);
p5.h = hi(TIMER_ENABLE);
p5.l = lo(TIMER_ENABLE);
/* clear interrupt request */
r7.h = hi(TIMIL5);
r7.l = lo(TIMIL5);
[p5 + TIMER_STATUS - TIMER_ENABLE] = r7;
/* toggle width values (width = period - width) */
r7 = [p5 + TIMER5_PERIOD - TIMER_ENABLE];
r6 = [p5 + TIMER5_WIDTH - TIMER_ENABLE];
r5 = r7 - r6;
[p5 + TIMER5_WIDTH - TIMER_ENABLE] = r5;
r5 = [p5 + TIMER4_WIDTH - TIMER_ENABLE];
r7 = r7 - r5;
CC = r7 < 0;
if CC r7 = r6;
[p5 + TIMER4_WIDTH - TIMER_ENABLE] = r7;
/* disable after a certain number of periods */
r0+= -1;
CC = r0 == 0;
ADSP-BF537 Blackfin Processor Hardware Reference
General-Purpose Timers
15-59