The program runs in external flash

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Hi,

  Please answer the following questions：   

1.Nrf52 series, can the program run on external flash?Flash is the SPI interface.

2.If it can run on external flash, what are the requirements for flash type selection and how to set it so that the program can run on flash?

3.Does flash with external SPI have requirements for the selection of SPI interface of the chip?

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Please help to have a look，Thanks!