Power Management
15-21
Clock Generation and System Reset Management
15.3 Power Management
There are three clock domains in the OMAP5910 device. Each clock domain
has its own clock management unit and can be put into idle mode (power sav-
ing mode) when unused without affecting the rest of OMAP5910 device
functionality. In addition, the ULPD provides low-power modes that affect the
entire device, not just the individual domains (see Figure 15–10).
A chip idle occurs when the DSP is idled, the MPU requests an idle, and the
TC domain has no remaining transactions. Chip idle causes the ULPD to initi-
ate big sleep mode. In big sleep mode, DPLL 1 is turned off, but the 12-MHz
clock is still active. If the 12-MHz clock is not needed, then the ULPD can
initiate a further transition to deep sleep mode, which turns the 12-MHz clock
off internally.
When an unmasked interrupt event occurs, a request is performed by the
wake-up control module. When receiving the request, if the device is in deep
sleep mode, the ULPD brings the device out of deep sleep mode. Once the
12-MHz clock is stable, the ULPD brings the device into awake mode.
To reduce the wake-up time, a special hardware request is implemented in
parallel to interrupts to wake-up the ULPD whenever an interrupt occurs. This
request is generated by peripherals as USB or UART. When receiving the
hardware request, the ULPD brings the device out of the deep sleep mode to
wakeup the 12-MHz clock. When the clock is awake, the ULPD goes to big
sleep and awakes if a request is received from wake-up control module.
Figure 15–11 shows the wakeup control module.
Deep sleep mode is the entry state of the device when a power-on reset
occurs. Such a reset acts as a wake-up request, causing the device to
transition to the awake state.
The 12-MHz clock may be required to clock signals out of the device (such as
the MCLK pin) or to ULPD DPLL (used for USB and other internal peripherals)
in either the big sleep or awake states. The deep sleep state can not be entered
if there is need for the 12-MHz clock.
The power management state machine runs at 32 kHz. All control signals of
this state machine are resynchronized on the 32-kHz clock. The 32-kHz clock
is always on.
Table 15–3 lists the peripherals and external signals which can wake up
OMAP5910 from deep sleep.