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S3F80JB CLOCK CIRCUITS
7-1
7 CLOCK CIRCUITS
OVERVIEW
The clock frequency for the S3F80JB can be generated by an external crystal or supplied by an external clock
source. The clock frequency for the S3F80JB can range from 1MHz to 8 MHz. The maximum CPU clock
frequency, as determined by CLKCON register, is 8 MHz. The X
IN
and X
OUT
pins connect the external oscillator
or clock source to the on-chip clock circuit.
SYSTEM CLOCK CIRCUIT
The system clock circuit has the following components:
— External crystal or ceramic resonator oscillation source (or an external clock)
— Oscillator stop and wake-up functions
— Programmable frequency divider for the CPU clock (f
OSC
divided by 1, 2, 8, or 16)
— Clock circuit control register, CLKCON
X
IN
X
OUT
C1
C2
Figure 7-1. Main Oscillator Circuit
(External Crystal or Ceramic Resonator)
X
IN
X
OUT
External
Clock
Open Pin
Figure 7-2. External Clock Circuit