ATAR092 datasheet(14/100 Pages) ATMEL

14 / 100 page

ATAR092/ATAR892

4535C–4BMCU–02/04

The clock module is programmable via software with the clock management register

(CM) and the system configuration register (SC). The required oscillator configuration

can be selected with the OS1-bit and the OS0-bit in the SC-register. A programmable 4-

bit divider stage allows the adjustment of the system clock speed. A special feature of

the clock management is that an external oscillator may be used and switched on and

off via a port pin for the power-down mode. Before the external clock is switched off, the

internal RC-oscillator 1 must be selected with the CCS-bit and then the SLEEP mode

may be activated. In this state an interrupt can wake up the controller with the RC-oscil-

lator, and the external oscillator can be activated and selected by software. A

synchronization stage avoids too short clock periods if the clock source or the clock

speed is changed. If an external input clock is selected, a supervisor circuit monitors the

external input and generates a hardware reset if the external clock source fails or drops

below 500 kHz for more than 1 ms.

Figure 14.

Clock Module

The clock module generates two output clocks. One is the system clock (SYSCL) and

the other the periphery (SUBCL). The SYSCL can supply the core and the peripherals

and the SUBCL can supply only the peripherals with clocks. The modes for clock

sources are programmable with the OS1-bit and OS0-bit in the SC-register and the

CCS-bit in the CM-register.

Ext. clock

ExIn

ExOut

Stop

RC oscillator2

RCOut2

Stop

Trim

4-MHz oscillator

4Out

Stop

Oscin

Oscout

Oscin

Oscout

32-kHz oscillator

32Out

Oscin

Oscout

oscillator 1

RCOut1

Control

Stop

IN1

IN2

Cin

Divider

Sleep

WDL

Osc-Stop

NSTOP

CCS

CSS1

CSS0

CM:

BOT

- - -

OS1

OS0

SUBCL

SYSCL

OSC1

OSC2

mask option

Cin/16

32 kHz

Table 5.

Clock Modes

Mode

OS1

OS0

Clock Source for SYSCL

Clock Source

for SUBCL

CCS = 1

CCS = 0

RC-oscillator 1 (internal)

External input clock

in/16

RC-oscillator 1 (internal)

RC-oscillator 2 with

external trimming resistor

in/16

RC-oscillator 1 (internal)

4-MHz oscillator

in/16

RC-oscillator 1 (internal)

32-kHz oscillator

32 kHz

ATAR092 Datasheet(PDF) 14 Page - ATMEL Corporation

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