Page 45 - Embedded Microprocessor Systems Real World Design
P. 45
SINGLE IC
MULTIPLE IC
I/O TO EXTERNAL
MICROPROCESSOR I - FORTS DEVICES
CRYSTAL
U CORE I
DASHED LINES INDICATE FUNCTIONALIM
CONTAINED IN MICROPROCESSOR IC.
Figure 2.1
Single and Multiple IC Microprocessor Circuits.
turer's data sheets. If you are using an external clock source, such as a packaged
oscillator, make sure it meets the voltage and capacitance drive specifications of the
processor.
Some microcontrollers, such as the Atmel ATTiny series, have internal R-C oscil-
lators and do not need any external clock. However, the R-C oscillators are not as
stable or as accurate as a crystal or ceramic resonator. Some microcontrollers with
internal oscillators improve clock accuracy by providing a means to calibrate the
frequency, but the result is still not as stable as a crystal.
30 Embedded Miwo$n-ocessm System
