RM0312 datasheet(90/275 Pages) STMICROELECTRONICS

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Beeper (BEEP)

RM0312

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DocID022352 Rev 3

Beeper (BEEP)

13.1

Introduction

This function generates a beep signal in the range of 1, 2 or 4 kHz when the LS clock is

operating at a frequency of 38 kHz.

Figure 15. Beep block diagram

13.2

Beeper functional description

13.2.1

Beeper operation

To use the beep function, perform the following steps in order:

Calibrate the LS clock frequency as described in Section 13.2.2: Beeper calibration to

define BEEPDIV[4:0] value.

Select 1 kHz, 2 kHz or 4 kHz output frequency by writing to the BEEPSEL[1:0] bits in

the Beeper control/status register (BEEP_CSR).

Set the BEEPEN bit in the Beeper control/status register (BEEP_CSR) to enable the

LS clock source.

Note:

The prescaler counter starts to count only if BEEPDIV[4:0] value is different from its reset

value, 0x1F.

BEEPEN

BEEP pin

LSI RC

38 kHz

MSR

to Timer Input Capture

5-BIT BEEPER PROG

COUNTER

~8 kHz

3-BIT COUNTER

1 kHz, 2 kHz, 4 kHz

(for measurement)

fLS

BEEPDIV[4:0] bits

BEEPSEL[1:0] bits

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