TSS461C datasheet(9/57 Pages) ATMEL

9 / 57 page

TSS461C

4193G–AUTO–12/04

Oscillator

An oscillator is integrated in the TSS461C, and consists of an inverting amplifier which

the input is XTAL1 and the output XTAL2.

A parallel resonance quartz crystal or ceramic resonator must be connected to these

pins. As shown in Figure 1, two capacitors have to be connected from the crystal pins to

ground. The values of C1 depend on the frequency chosen and can be selected using

the graphic given in Figure 33.

If the oscillator is not used, then a clock signal must be fed to the circuit via the XTAL1

input.

Note, that this pin will behave as a CMOS level compatible Schmitt trigger input. In this

case, the XTAL2 output should be left unconnected. The oscillator also features a buff-

ered clock output pin CKOUT. The signal on this pin is directly buffered from the XTAL1

input, without inversion.

There is one more pin used for the oscillator. The TEST/VSS pin is in fact its ground,

and unless this pin is firmly connected to ground, with decoupling capacitors, the oscilla-

tor will not operate correctly.

The test mode itself, i.e., when the TEST/VSS pin is held high, is only intended for fac-

tory use, and the functionality of this mode is not specified in any way.

Furthermore, it is subject to change without notice, the only exception is for incoming

inspection tests using the test program.

The clock signal is then fed to the clock generator generate all the necessary timing sig-

nals for the operation of the circuit. The clock generator is controlled by a 4-bit code

called the clock divider.

TSCLK

XTAL1

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