T48C862-R4 datasheet(29/107 Pages) ATMEL

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T48C862-R4 [Preliminary]

4551C–4BMCU–01/04

System Configuration

Primary register address: "3"hex

Table 7.

Oscillator Select

Power-down Modes

The sleep mode is a shut-down condition which is used to reduce the average system

power consumption in applications where the microcontroller is not fully utilized. In this

mode, the system clock is stopped. The sleep mode is entered via the SLEEP instruc-

tion. This instruction sets the interrupt enable bit (I) in the condition code register to

enable all interrupts and stops the core. During the sleep mode the peripheral modules

remain active and are able to generate interrupts. The microcontroller exits the sleep

mode by carrying out any interrupt or a reset.

The sleep mode can only be kept when none of the interrupt pending or active register

bits are set. The application of the $AUTOSLEEP routine ensures the correct function of

the sleep mode. For standard applications use the $AUTOSLEEP routine to enter the

power-down mode. Using the SLEEP instruction instead of the $AUTOSLEEP following

an I/O instruction requires to insert 3 non-I/O instruction cycles (for example NOP NOP

NOP) between the IN or OUT command and the SLEEP command.

The total power consumption is directly proportional to the active time of the microcon-

troller. For a rough estimation of the expected average system current consumption, the

following formula should be used:

total (VDD, fsyscl) = ISleep + (IDD

× t

active/ttotal)

DD depends on VDD and fsyscl

Bit 3Bit 2Bit 1Bit 0

SC: write

BOT

–

OS1

OS0

Reset value: 1x11b

BOT

Brown-Out Threshold

BOT = 1, low brown-out voltage threshold (1.7 V)

BOT = 0, high brown-out voltage threshold (2.0 V)

OS1

Oscillator Select 1

OS0

Oscillator Select 0

Mode

OS1

OS0

Input for SUBCL

Selected Oscillators

111

in/16

RC-oscillator 1 and external input clock

201

in/16

RC-oscillator 1 and RC-oscillator 2

310

in/16

RC-oscillator 1 and 4-MHz crystal oscillator

400

32 kHz

RC-oscillator 1 and 32-kHz crystal

oscillator

Note:

If bit CCS = 0 in the CM register the RC-oscillator 1 always stops.

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