4.7
XTAL2
Output from the inverting oscillator amplifier.
5. Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be
configured for use as an on-chip oscillator, as shown in
Either a quartz crystal or
ceramic resonator may be used. To drive the device from an external clock source, XTAL2
should be left unconnected while XTAL1 is driven as shown in
There are no require-
ments on the duty cycle of the external clock signal, since the input to the internal clocking
circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low
time specifications must be observed.
Figure 5-1.
Oscillator Connections
Note:
C1, C2 = 30 pF
±
10 pF for Crystals
= 40 pF
±
10 pF for Ceramic Resonators
Figure 5-2.
External Clock Drive Configuration
4
AT89C4051
1001F–MICRO–6/08
ATMEL [ ATMEL CORPORATION ]
