Rainbow Electronics AT89C4051 - Manual (Page 4)

4
AT89C4051
1001D–06/01
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 Figure 1. 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 Figure 2.
There are no requirements 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 1. Oscillator Connections
Note: C1, C2= 30 pF ± 10 pF for Crystals
= 40 pF
± 10 pF for Ceramic Resonators
Figure 2. External Clock Drive Configuration