Samsung 8-Bit CMOS Microcontroller, S3C9228/P9228 user manual Clock Circuits

S3C9228/P9228 CLOCK CIRCUITS

7 CLOCK CIRCUITS

OVERVIEW

The S3C9228 microcontroller has two oscillator circuits: a main clock, and a sub clock circuit. The CPU and peripheral hardware operate on the system clock frequency supplied through these circuits. The maximum CPU clock frequency, is determined by CLKCON register settings.

SYSTEM CLOCK CIRCUIT

The system clock circuit has the following components:

—Crystal, ceramic resonator, RC oscillation source (main clock only), or an external clock

—Oscillator stop and wake-up functions

—Programmable frequency divider for the CPU clock (fxx divided by 1, 2, 8, or 16)

—Clock circuit control register, CLKCON

—Oscillator control register, OSCCON

CPU CLOCK NOTATION

In this document, the following notation is used for descriptions of the CPU clock:

fx main clock

fxt sub clock

fxx selected system clock

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