EM6621 datasheet(28/69 Pages) EMMICRO

28 / 69 page

EM6621

03/02 REV. D/444

 2002, EM Microelectronic-Marin SA

www.emmicroelectronic.com

7.1.1 Single Run Mode

The RegMelPeri value and the selected timer frequency in RegMelTim control the timer duration. The timer is

counting down from its previously charged value until it reaches 0. On 0 the timer stops and generates an

interrupt request. The buzzer frequency output is enabled after the next positive timer clock edge and remains

enabled until the timer reaches 0.

7.1.2 Continuos Run Mode

This is almost the same as the single run mode only that in this case the timer after reaching 0 reloads itself

automatically with the register RegMelPeri value. Every time the timer reaches 0 an interrupt request is send.

There are 2 ways to stop the continuos mode.

•

First, changing the mode to single run mode. As the timer reaches 0 it stops. The last period after Auto=0 is

of length RegMelPeri + 1.

•

Second, loading 0 into the timer period register RegMelPeri stops the timer immediately, no interrupt is

generated and the Auto flag is reset. The buzzer frequency output is enabled directly by writing Auto=1.

Figure 20. Single Run Mode

µP writes 2 into

RegMelPeri

µP writes 1 into

RegMelP eri

Tim er Clock

Tim er Value

Buzzer

IRQBz

Figure 21. Continuos Run Mode

µP writes

Auto = 0

µP writes

Auto = 1

µP writes 2

into

RegMelPeri

Timer Clock

n periods

n+1 periods

Timer Value

Buzzer

IRQBz

EM6621 Datasheet(PDF) 28 Page - EM Microelectronic - MARIN SA

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