Hi Hui Shao,
Of course, the K20D50M support the VLPR mode and you can find the more detail information in the reference manual.
http://cache.nxp.com/files/32bit/doc/ref_manual/K20P64M50SF0RM.pdf?fpsp=1&WT_TYPE=Reference%20Manual...
The Kinetis SDK v1.3 Demo Application User's Guide includes the descriptions of the several demos, please take a moment to review it.
You can also go to download the sample code of the TWR-K20D50M through the link as below and it also contains the low power demo, I think it can be useful.
cache.nxp.com/files/32bit/software/KINETIS_50MHZ_SC.zip?fpsp=1&WT_TYPE=Lab%20and%20Test%20Software&W...
Hope it hleps
Have a great day,
Ping
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