Samsung S5PC110, Manual

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S5PC110_UM 4 POWER MANAGEMENT
4-25
4.6 WAKEUP SOURCES
Table 4-6 Relationship Among Power Mode Wakeup Sources
Power Mode Wakeup Sources
All interrupt sources
I2S (in audio block)
MMC0, MM1, MMC2, MMC3
TSADC
System
Timer
External interrupt sources (EINT)
RTC Alarm
RTC TICK
KEYIF
IDLE
DEEP-IDLE
(1)
DEEP-IDLE
(2)
STOP
or
DEEP-
STOP
SLEEP
HDMI CEC
NOTE:
1. If TOP block on
2. If TOP block off
4.6.1 EXTERNAL INTERRUPTS
External interrupts are the common wake-up source of IDLE (including DEEP-IDLE), STOP (including DEEP-
STOP), and SLEEP modes. The logic for external interrupt configuration such as polarity, edge/level sensitivity,
and masking resides in the GPIO. It can be modified through GPIO register setting before entering power down
modes. The external interrupt handling logic holds the external interrupt information until Cortex-A8 clears the
information. It allows Cortex-A8 to handle the external interrupt after wake-up.
4.6.2 RTC ALARM
The Real Time Clock (RTC) has 32-bit counter to wake up the system after specified time. If the timer alarm
triggers, the SYSCON wakes up the system and sets the RTL_ALARM field of WAKEUP_STAT register to 1. After
the wake-up, Cortex-A8 can refer the WAKEUP_STAT register to find out the cause of wake up.
4.6.3 SYSTEM TIMER
System Timer is newly introduced module in S5PC110. It supplements PWM timer, which suffers from
accumulation of time deviation when operated in variable tick mode. On the contrary, System Timer is free from
such deviation and can be a preferrable choice for variable tick generation.
In DEEP-IDLE, STOP, and DEEP-STOP mode, there can be no system clock when TOP block is power-gated.
Therefore, RTC is used to generate timing tick instead of PWM timer, but by using this clock, timing count is not
controlled to meet exact 1ms OS time tick since RTC clock does not have high resolution. On the other hand,
System timer has the function to generate interrupts at various interval, and do not require manual setting. Thus, it
does not wake up the chip too often, and provides accurate 1ms timing ticks. It uses an external crystal clock,
RTC clock and the generated clock from SYSCON as clock input.
For System Timer to operate in DEEP-IDLE, STOP, and DEEP-STOP mode, power to System Timer is not gated.
The wakeup event from System Timer will wake up S5PC110 from DEEP-IDLE, STOP, and DEEP-STOP mode.