T48C862x-Rf-TNQ datasheet(26/107 Pages) ATMEL

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T48C862-R4 [Preliminary]

4551C–4BMCU–01/04

Figure 21.

RC-oscillator 1

External Input Clock

The OSC1 or OSC2 (mask option) can be driven by an external clock source provided it

meets the specified duty cycle, rise and fall times and input levels. Additionally, the

external clock stage contains a supervisory circuit for the input clock. The supervisor

function is controlled via the OS1, OS0 bit in the SC register and the CCS bit in the

CM register. If the external input clock is missing for more than 1 ms and CCS = 0 is set

in the CM register, the supervisory circuit generates a hardware reset.

Figure 22.

External Input Clock

Table 5.

Supervisor Function Control Bits

RC-oscillator 2 with External

Trimming Resistor

The RC-oscillator 2 is a high resolution trimmable oscillator whereby the oscillator fre-

quency can be trimmed with an external resistor between OSC1 and V

DD. In this

configuration, the RC-oscillator 2 frequency can be maintained stable with a tolerance of

±10% over the full operating temperature and a voltage range V

DD from 2.5 V to 6.0 V.

For example:

An output frequency at the RC-oscillator 2 of 2 MHz can be obtained by connecting a

resistor R

ext = 360 kΩ (see Figure 23 on page 27).

oscillator 1

RcOut1

Stop

Control

RcOut1

Osc-Stop

OS1

OS0

CCS

Supervisor Reset Output (Res)

110

Enable

111

Disable

Ext. input clock

ExOut

Stop

Ext.

Clock

RcOut1

Osc-Stop

ExIn

CCS

Res

OSC1

OSC2

Clock monitor

Ext.

Clock

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