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S3C2440A RISC MICROPROCESSOR CLOCK & POWER MANAGEMENT
7-15
SLEEP Mode
The block disconnects the internal power. So, there occurs no power consumption due to CPU and the internal
logic except the wake-up logic in this mode. Activating the SLEEP mode requires two independent power sources.
One of the two power sources supplies the power for the wake-up logic. The other one supplies other internal
logics including CPU, and should be controlled for power on/off. In the SLEEP mode, the second power supply
source for the CPU and internal logics will be turned off. The wakeup from SLEEP mode can be issued by the
EINT[15:0] or by RTC alarm interrupt.
Follow the Procedure to Enter SLEEP mode
1. Set the GPIO configuration adequate for SLEEP mode.
2. Mask all interrupts in the INTMSK register.
3. Configure the wake-up sources properly including RTC alarm. (The bit of EINTMASK corresponding to the
wake-up source has not to be masked in order to let the corresponding bit of SRCPND or EINTPEND set.
Although a wake-up source is issued and the corresponding bit of EINTMASK is masked, the wake-up will
occur and the corresponding bit of SRCPND or EINTPEND will not be set.)
4. Set USB pads as suspend mode. (MISCCR[13:12]=11b)
5. Save some meaning values into GSTATUS[4:3] register. These register are preserved during SLEEP mode.
6. Configure MISCCR[1:0] for the pull-up resisters on the data bus,D[31:0]. If there is an external BUS holder,
such as 74LVCH162245, turn off the pull-up resistors. If not, turn on the pull-up resistors.
Additionally, The Memory concerning pins is set to two types, one is Hi-z, and the other is Inactive state.
7. Stop LCD by clearing LCDCON1.ENVID bit.
8. Read rREFRESH and rCLKCON registers in order to fill the TLB.
9. Let SDRAM enter the self-refresh mode by setting the REFRESH[22]=1b.
10. Wait until SDRAM self-refresh is effective.
11. Set MISCCR[19:17]=111b to make SDRAM signals(SCLK0,SCLK1 and SCKE) protected during SLEEP mode
12. Set the SLEEP mode bit in the CLKCON register.
Caution: When the system is operating in NAND boot mode, The hardware pin configuration - EINT[23:21] – must
be set as input for starting up after wakeup from sleep mode.