topic Re: Wait and Stop Mode - How to enter and exit KEA in Kinetis Microcontrollers

Wait and Stop Mode - How to enter and exit KEA

kaslewis — Sun, 14 Dec 2014 16:34:42 GMT

Hello,

How do I enter and exit the wait and stop power modes on the KEA. I am looking to be able to go into a low or very low power mode and wait for an external interrupt, the external interrupt should wake the KEA and put it back in full power mode till the task is completed and then the KEA should go back to low power mode. I would also like to know which interrupt pin caused the KEA to wake.

Thanks

Kas

Re: Wait and Stop Mode - How to enter and exit KEA

mjbcswitzerland — Sun, 14 Dec 2014 17:12:47 GMT

Kas

WAIT mode is entered by executing the Cortex WFI instruction [__asm__("wfi")]. Any interrupt will wake from this mode since peripherals and clocks remain functional.

STOP mode is entered by executing the same instruction but first setting the SLEEPDEEP bit in the Cortex SYSTEM_CONTROL_REGISTER. In the STOP mode there are various settings that can be used in the Kinetis derivative to control which clocks remain enabled (this is part specific so you need to look through the power management section of the manual for your specific device).
In the STOP mode the KBI and IRQ pins can be used to wake-up.

Regards

Mark

Re: Wait and Stop Mode - How to enter and exit KEA

yasuhikokoumoto — Mon, 15 Dec 2014 02:34:01 GMT

Hi Kas,

the Sleep-on-Exit mode would be the best for your solution. In this mode, the CPU always resides in WAIT mode and waking up by an interrupt to enter the correspondent ISR, and enters WAIT mode after exiting the ISR. To enable the Sleep-on-Exit mode, you first set SCR.SLEEPONEXIT=1 and by executing WFI instruction to enter the Sleep-on-Exit mode. Regarding the Sleep-on-Exit, please refer to the article http://my.safaribooksonline.com/book/electrical-engineering/computer-engineering/9780123854773/chapter-17dot-using-low-power-features-in-programming/using_the_sleeponexit_feature.
As for the interrupt, you can choose one of the 16 keyboard interrupts (if KEA128 then 64) and an IRQ (PTA5).

Best regards,
Yasuhiko Koumoto.