T48C893 datasheet(48/82 Pages) ATMEL

48 / 82 page

T48C893

Rev. A4, 22-Jan-02

48 (82)

Timer 3 – Mode 12: Timer / counter with external capture mode (T3I)

The counter is driven by an internal clock source and an edge at the external input T3I loads the counter value into the

capture register. The edge can be selected with the programmable edge detector of the timer input stage. This mode

can be used for signal and pulse measurements.

01 2 3456 7 8 9 1011

Counter 3

T3CP–

13819

T3I

T3R

Capture value = X

Capture value = 17

Capture

value = 35

121314 16

171819

21 23

242526

28 30

313233

35 37

383940

Figure 55. External capture mode

Timer 3 Modulator for Carrier Frequency Burst Modulation

If the output stage operates as pulse-width modulator for the shift register the output can be stopped with stage 1 of

Timer 2. For this task, the timer mode 3 must be used and the prescaler must be supplied by the internal shift clock

of the shift register.

The modulator can be started with the start of the shift register (SIR=0) and stopped either by a shift register stop

(SIR=1) or compare match event of stage 1 of Timer 2. For this task, the Timer 2 must be used in mode 3 and the pre-

scaler stage must be supplied by the internal shift clock of the shift register.

13820

Set

Res

T3O

T3TOP

OMSK

TOG3

SSI/

Control

MUX

T3M

Timer 3 Mode

T3O

MUX 1

MUX 2

MUX 3

other

MUX 0

Figure 56. Modulator 3

Timer 3 Demodulator for Biphase, Manchester and Pulse-Width-Modulated Signals

The demodulator stage of Timer 3 can be used to decode Biphase, Manchester and pulse-width-coded signals

Demodulator 3

T3EX

Res

CM31

Counter 3

Reset

Counter 3

Control

SCI

T3I

T3M

13821

Figure 57. Timer 3 demodulator 3

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