AT90S/LS2333 and AT90S/LS4433
5
Clock Options
Crystal Oscillator
XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be configured for use as an on-
chip oscillator, as shown in Figure 2 and Figure 3. Either a quartz crystal or a ceramic resonator may be used.
External Clock
If the oscillator is to be used as a clock for an external device, the clock signal from XTAL2 may be routed to one HC buffer,
while reducing the load capacitor by 5 pF, as shown in Figure 3. To drive the device from an external clock source, XTAL2
should be left unconnected while XTAL1 is driven as shown in Figure 4.
Figure 2. Oscillator Connections
Figure 3. Using MCU Oscillator as a Clock for an External Device
Figure 4. External Clock Drive Configuration
XTAL1
REDUCE BY 5
P
F
MAX 1 HC BUFFER
XTAL2
HC
