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14.6.3 Power Domain Transition Control
The Device has multiple power domains. All these power domains will be controlled by on-chip power
switches.
14.6.3.1 Power-Down Sequence
Power-down sequence defined here assumes that IP with STANDBY interface is already in
smart-standby mode and STANDBY is already asserted by the IP.
1. Software will request PRCM to put all modules in the specific power domain in "Disable" by
programming "Module control Register: Disable" inside PRCM, i.e., CM_<Power
domain>_<module>_CLKCTRL[x] MODULEMODE = 0 (DISABLED).
2. PRCM starts the power management handshake (IdleReq/IdleAck) with IPs.
3. FCLKEN will be driven LOW by PRCM. PRCM will gate-off all the clock to the functional clock
domains.(ICLK and FCLK).
4. Software will request PRCM to put all Interface clock domains in the specific power domain in "force
sleep" by programming "Functional clock Domain control register: force sleep" inside PRCM, i.e.,
CM_<Clock domain>_CLKSTCTRL[x] CLKTRCTRL = 1 (SW_SLEEP)
5. Software will request PRCM to put a specific power domain in OFF state by programming MMR
(PWRSTCTRL: OFF ) inside PRCM. PM_<Power domain>_PWRSTCTRL[POWERSTATE] = 0
(OFF).
6. Specific PSCON inside PRCM will assert the control signals for enabling Isolation cells.
7. PRCM asserts reset of the domain.
8. PSCON then will assert control signal to switch-off the actual power supply.
9. On Die switch will control the actual power supply to the Domain and the acknowledgement is fed
back to PRCM.
14.6.3.2 Power-Up Sequence
1. One of the Always on domain IPs send a wake-up interrupt to the Cortex™-A8. [All IPs that can
generate wake-up are always enabled].
2. Software will request PRCM to put all Interface clock domains in the specific power domain in "force
wakeup" by programming "Functional clock Domain control register: force wakeup" inside PRCM,
i.e., CM_<Clock domain>_CLKSTCTRL[x] .CLKTRCTRL = 2h (SW_WKUP).
3. This will enable power as well as interface clocks.
4. Specific PSCON inside PRCM will assert the control signals to switch-on the actual power supply.
5. This On Die power switch will switch ON the power supply to the domain.
6. Once the power supply is switched ON, acknowledgement is fed back to PSCON.
7. PRCM de-asserts reset of the domain.
8. PRCM will then turn-off isolation cells.
9. Software will request PRCM to put all modules in the specific power domain in "Enable" by
programming "Module control Register: Enable" inside PRCM, i.e., CM_<Power
domain>_<module>_CLKCTRL[x] MODULEMODE = 2h (ENABLED).
10. PRCM will de-assert the "IdleReq" to the modules
NOTE:
•
If only modules need to be disabled, then only power-down sequence steps 1, 2, 3
will be performed. (PRCM will clock gate clocks to the module, if all modules sharing
that clock are disabled).
•
Programming "PWRSTCTRL" can be skipped in both the sequnces. In such a
scenario PWRSTCTRL:OFF should be in default state. Whenever Functional clock
Domain control register: force sleep is programmed, it will automatically go to OFF
state. Whenever Functional clock Domain control registers: force wakeup is
programmed, it will automatically go to ON state.
•
PWRSTCTRL: ON should be programmed only if there is any requirement of not to
switch off the power but gate all the clocks.
SPRUGX9 – 15 April 2011
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Preliminary
Power, Reset, and Clock Management (PRCM) Module
© 2011, Texas Instruments Incorporated
Power Management
1423
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