ATAR092-C_14 Datasheet, PDF(15/108 Page) ATMEL Corporation – Up to 7 External/Internal Interrupt Sources

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ATAR092-C_14 Datasheet, PDF (15/108 Pages) ATMEL Corporation – Up to 7 External/Internal Interrupt Sources

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ATAR092-C/ATAR892-C

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-oscillator, 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 4-12. Clock Module

OSC1

OSC2

Oscin

Ext. clock

ExIn

ExOut

Stop

RC oscillator2

RTrim

RCOut2

Stop

4-MHz oscillator

Oscin

Oscout

4Out

Stop

32-kHz oscillator

Oscout Oscin

Oscout

32Out

oscillator 1

Stop

IN1

RCOut1

Control

IN2

Cin

Divider

Osc-Stop

Sleep

WDL

CM NSTOP CCS CSS1 CSS0

mask option

SC BOT - - - OS1 OS0

Cin/16

32 kHz

SYSCL

SUBCL

Table 4-4. Clock Modes

Mode

OS1

OS0

Clock Source for SYSCL

CCS = 1

CCS = 0

Clock Source for

SUBCL

RC-oscillator 1 (internal)

External input clock

RC-oscillator 2 with external

trimming resistor

Cin/16

RC-oscillator 1 (internal)

4-MHz oscillator

32-kHz oscillator

Cin/16

32 kHz

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.

4593Dâ4BMCUâ05/06

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