CLOCK CIRCUIT

S3C84E5/C84E9/P84E9

 

 

CLOCK STATUS DURING POWER-DOWN MODES

The two power-down modes, Stop mode and Idle mode, affect the system clock as follows:

In Stop mode, the main oscillator is halted. Stop mode is released, and the oscillator is started, by a reset operation or an external interrupt (with RC delay noise filter), and can be released by internal interrupt too when the sub-system oscillator is running and watch timer is operating with sub-system clock.

In Idle mode, the internal clock signal is gated to the CPU, but not to interrupt structure, timers and timer/ counters. Idle mode is released by a reset or by an external or internal interrupt.

INT

 

Stop Release

 

 

 

 

 

 

 

 

 

 

 

 

 

Driving Ability

 

 

 

 

 

 

OSCCON.4

Main-System

fX

 

 

fXT

Sub-system

Watch Timer

Oscillator

 

 

Oscillator

 

 

 

 

 

Circuit

 

 

 

 

Circuit

 

 

 

Selector 1

 

 

 

 

 

 

fXX

 

 

 

Stop

 

 

 

 

 

 

OSCCON.3

 

 

 

 

 

 

OSCCON.0

 

 

 

 

Stop

OSCCON.2

 

 

 

 

 

STOP OSC

 

1/8-1/4096

 

Basic Timer

 

inst.

 

Frequency

 

Timer/Counter

 

 

 

 

Watch Timer (fxx/256)

 

 

 

Dividing

 

 

STPCON

 

 

 

 

 

Circuit

 

UART

 

 

 

 

 

 

1/1

1/2

1/8

1/16

A/D Converter

 

 

 

 

 

 

 

 

 

System Clock

 

CLKCON.4-.3

 

Selector 2

 

 

 

 

 

 

 

 

 

CPU Clock

 

 

 

 

 

IDLE Instruction

 

Figure 7-3. System Clock Circuit Diagram

7-2

Page 216
Image 216
Samsung S3C84E5 user manual Clock Status During POWER-DOWN Modes, System Clock Circuit Diagram