Public Version
PRCM Functional Description
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3.5.7.3.2 Wake-Up Sequences (Transition From Retention/Off to On)
The PRM detects a wake-up event from the daisy chain. Several wake-up events can occur
simultaneously, but PRM only sees the ORing of them. Depending on whether the CORE power domain is
in RETENTION or OFF state, the following sequence is followed to wake up the CORE and MPU power
domains:
1. When the CORE power domain wakes up from OFF/RETENTION power state, reset is asserted for
both the MPU and the CORE power domains.
2. The MPU and the CORE power domains are switched to ON power state.
3. The domain clocks of the MPU and the CORE power domains are restarted.
4. If the CORE power domain was in OFF power state, its reset is released before the MPU power
domain.
•
Hardware restores the I/O pad configuration and some configuration registers of the control
module. This configuration has been saved in the scratchpad memory (by the control module save
procedure initiated by software control prior to the transition to OFF power state).
•
The PRCM module switches the I/O pad configurations to the normal restored configuration (The
I/O pad isolation is released).
•
The reset is released for MPU power domain.
5. If the CORE power domain was in RETENTION power state, the reset is released for both the MPU
and the CORE power domains at the same time.
6. When the MPU boots, software accesses the SCM to read the wake-up event source (identified by the
CONTROL.CONTROL_PADCONF_< IOpad>[15] WAKEUPEVENT bits in the SCM corresponding to
all enabled pads).
7. Software disables the wake-up daisy chain by clearing the PRCM.
[8] EN_IO bit and
the PRCM.
[16] EN_IO_CHAIN bit.
NOTE:
A daisy-chain wake-up event always causes the MPU to restart and boot. Other
independent wake-up events activated in off mode (for example, a GPIO wake-up event)
always cause the CORE power domain to be activated. The MPU is wakened if a wake-up
dependency has been set by the user, or if the modem generates an interrupt to the MPU.
3.5.7.4
Device Off-Mode Sequences
Device off-mode sequencing requires preliminary settings that can be done during device initialization.
The following actions are performed once and remain valid for all device off/on transitions:
1. Configure valid off and active pad configuration for each pad by programming the SCM
CONTROL.CONTROL_PADCONF_< IOpad> register.
2. Save the active pad configuration by asserting the CONTROL.CONTROL_PADCONF_OFF[1]
STARTSAVE bit in the SCM. This process can be repeated each time the active pad configuration of
the device is changed.
3. Set the SCM to smart-idle mode by configuring the CONTROL. CONTROL_SYSCONFIG[4:3]
IDLEMODE bit field. This ensures that the module clocks remain active during the configuration save
procedure.
4. Disable all the modules running on system clock or switch them on the 32 kHz clock when required.
5. Configure the voltage regulator setup times (the PRCM.
[15:0] SETUP_TIME1 and
PRCM.
[31:16] SETUP_TIME2 bit fields).
6. Set sys_off_mode deassertion time in the PRCM.
[15:0] OFFSET_TIME bit field.
7. Configure the system clock oscillator setup time in the PRCM.
[15:0] SETUP_TIME
bit field.
For information about the SCM, see
, System Control Module.
3.5.7.4.1 Sleep Sequences
The sleep sequences exemplify the two types of device transitions from ON to OFF mode:
•
Device off-mode transition without using the SYS_OFF_MODE signal
394
Power, Reset, and Clock Management
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated
