AT89C4051_01 ATMEL [ATMEL Corporation], AT89C4051_01 Datasheet - Page 4

• Manufacturer Part Number: AT89C4051_01
• Description: 8-bit Microcontroller with 4K Bytes Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Oscillator
Characteristics
4
AT89C4051
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:
Figure 2. External Clock Drive Configuration
C1, C2= 30 pF ± 10 pF for Crystals
= 40 pF ± 10 pF for Ceramic Resonators
1001D–06/01