Motorola DSP96002 User Manual

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MOTOROLA

6.7.4

Pulse width measurement mode (mode 4)

The following program illustrates the use of the timer module for input pulse width mea-
surement. The width is measured in this example for the low active period of the input
pulse on the TIO1 pin and is stored in a table (in multiples of the chip operating clock di-
vided by 2).

org x:$100

; define buffer in X memory internal

pulse_width

$100

; measure up to 256 pulses

org p:$16

; this is timer1 interrupt vector address

movep x:TCR1,x:(r0)+

; store width value in table

nop

; second word of the short interrupt

....

org p:main_body

.....

move #pulse_width,r0

; r0 points to start of table

move #$ff,m0

; modulo 100 to wrap around on end of table

movep #$70000000,x:TCSR1

; enable timer interrupts, mode 4 and set INV

; to measure the low active pulse

bset #26,x:IPR

; enable IPL for timer 1

andi #$cf,mr

; remove interrupt masking in status register

bset #31,x:TCSR1

; timer enable

......

; do other tasks

.....