Taskit ARM9 CPU-module with Linux Stamp9261-series Stamp9261 (64F/64R) 542310 データシート
製品コード
542310
4.30. Power Management
Using power management can dramatically reduce the power consumption of an Embedded Device.
We assume that almost no application will use the maximum performance of the CPU and the
peripherals all of the time. The following possibilities for power management are available on the
Stamp9261:
We assume that almost no application will use the maximum performance of the CPU and the
peripherals all of the time. The following possibilities for power management are available on the
Stamp9261:
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switching off the TFT supply voltage
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putting the SDRAM into self-refresh mode
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putting the Ethernet controller in power down mode
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stopping the PLLs (PLLA and / or PLLB)
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stopping the clocks of the various peripherals
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reducing the clock rates of peripherals, especially by changing MCK.
a) Beware of tampering with the LCDC !
It is not recommended to reduce the clock speed of the LCD controller. Instead, the LCDC clock
should be stopped and the power supply for the LCD switched off, as otherwise the LCD can be
damaged.
It is not recommended to reduce the clock speed of the LCD controller. Instead, the LCDC clock
should be stopped and the power supply for the LCD switched off, as otherwise the LCD can be
damaged.
b) Idle Mode
In idle mode, the processor clock will be re-enabled by any interrupt. The peripherals, however, are
only able to generate an interrupt if they still have a clock, so care has to be taken as to when a
peripheral can be powered down.
In idle mode, the processor clock will be re-enabled by any interrupt. The peripherals, however, are
only able to generate an interrupt if they still have a clock, so care has to be taken as to when a
peripheral can be powered down.
It should also be taken into account that when a PLL is stopped it will take some time to restart it.
Changing the PLL frequencies or stopping them can therefore be done only at a moderate rate. If
short reaction times are required, this is not a choice.
Changing the PLL frequencies or stopping them can therefore be done only at a moderate rate. If
short reaction times are required, this is not a choice.
c) Slowing down MCK
However, in many cases a system waits for a user action or some other rare event. In such a case, it
is possible to change MCK to SLCK. Any external event which changes the state on peripheral pins
(not the USB) can then be detected by the PIO controller or the AIC.
However, in many cases a system waits for a user action or some other rare event. In such a case, it
is possible to change MCK to SLCK. Any external event which changes the state on peripheral pins
(not the USB) can then be detected by the PIO controller or the AIC.
d) Low Power SDRAM
The Stamp9261 makes use of Low Power (Mobile) SDRAM. The enhanced low power features of the
SDRAM controller are thus available:
The Stamp9261 makes use of Low Power (Mobile) SDRAM. The enhanced low power features of the
SDRAM controller are thus available:
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deep power down (all SDRAM data is lost)
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partial self-refresh (only part of the SDRAM is refreshed, data of all other parts is lost).
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