Samsung SC32442B54, User Manual

Page: 224 / 647

SC32442B RISC MICROPROCESSOR CLOCK & POWER MANAGEMENT
7
-
15
STOP Mode
In STOP mode, all clocks are stopped for minimum power consumption. Therefore, the PLL and oscillator circuit
are also stopped. Just after exiting the STOP mode, only NORMAL mode is available. In Figure 7-13-1, the user
must return from STOP mode to NORMAL mode. To exit from STOP mode, EINT, TICK or RTC alarm has to be
activated and CLKCON register is set properly.
DRAM has to be in self-refresh mode during STOP mode to retain valid memory data.
LCD must be stopped before STOP mode, because DRAM can't be accessed when it’s in self-refresh mode.
All interrupts should be masked, because DRAM can't be accessed when it’s in self-refresh mode.
(Even though all interrupts are masked, EINT can wake-up SC32442B with the setting of EXINT register.)
The SC32442B can exit from STOP mode by EINT(external interrupts), TICK or RTC alarm. During the wake-up
sequences, the crystal oscillator and PLL may begin to operate. The lock time is also needed to stabilize FCLK.
The lock time is inserted automatically and guaranteed by power management logic. During this lock time the
clock is not supplied. Just after wake-up sequences wake-up interrupt(RTC alarm, TICK or external interrupt) is
requested. The mode returns to normal mode re-written into the CLKCON register, immediately, [rCLKCON[0]=1]
XTIpll
or
EXTCLK
Wake-up
VCO
Output
Clock
Disable
FCLK
several slow clocks
(XTIpll or EXTCLK)
STOP mode is initiated.
lock time
Figure7-12. Entering STOP Mode and Exiting STOP mode (Wake-up)
If you know TICK wake-up source, RTC clock enabled once escape STOP mode
(Exit STOP mode, set CLKCON [14] immediately)