CLOCK CIRCUITS
S3C80A5B
7-2
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 started, by Power On
Reset operation or by a non-vectored interrupt - interrupt with reset (INTR). To enter the Stop mode, STOPCON
(STOP Control register) has to be loaded with value, #0A5H before STOP instruction execution. After recovering
from the Stop mode by reset or interrupt, STOPCON register is automatically cleared.
— In Idle mode, the internal clock signal is gated away from the CPU, but continues to be supplied to the interrupt
structure, timer 0, and counter A. Idle mode is released by a reset or by an interrupt (external or internally
generated).
Main
OSC
STOP
Instruction
Noise
filter
Oscillator
Stop
Oscillator
Wake-up
INT Pin
(1)
1/16
1/2
1/8
M
U
X
CLKCON.3,.4
STOPCON
CPU
Clock
NOTES:
1. An external interrupt with an RC-delay noise filter (for S3C80A4A/C80A8A/
C80A5A, INT0-4) is fiexed to release
Stop mode and "wake up" the main oscillator.
2. Because the S3C80A5B has no subsystem clock,
the 3-bit CLKCON signature code (CLKCON.2-CLKCON.0) is no meaning.
Figure 7-3. System Clock Circuit Diagram