nRF52840 QSPI XIP and standby

RE: nRF52840 QSPI XIP and standby

Kenneth — Thu, 26 Apr 2018 07:41:29 GMT

Hi, QSPI will not go into standby and also the external Flash will not go into standby since the CSN line is kept low by the peripheral. A timeout that puts the QSPI into standby when there is no XiP operation for a certain time is a good feature request, but not implemented in any product so far.

The only workaround that we could imagine is to use a timer/RTC as a watchdog. The CPU needs to clear/restart it from time to time. If it timeout it can trigger TASKS_DEACTIVATE on the QSPI. But then there also needs to be code to activate and initialize it again. Not very nice, but maybe worth for long times between XiP accesses.

RE: nRF52840 QSPI XIP and standby

changjo — Wed, 25 Apr 2018 19:37:39 GMT

I want to elaborate that I am trying to conserve power. I would like to know the expected behavior of the QSPI XIP peripheral after doing xip operation. Specifically does the QSPI peripheral go into standby mode between xip operations? If not is there a workaround fix that can get the QSPI to do standby?

RE: nRF52840 QSPI XIP and standby

changjo — Fri, 20 Apr 2018 22:42:42 GMT

For the application, the execute in place may be used for indeterminate amount of time depending on how much code will be off loaded. Therefore knowing when to uninit or put deep power down mode will be difficult. Also to put deep sleep or uninit in every location would be quite a task. If there was a work around that the QSPI can self managed is something more preferable.

RE: nRF52840 QSPI XIP and standby

run_ar — Thu, 19 Apr 2018 10:22:26 GMT

The best solution would be to uninit QSPI when it is not in use. You could also test deep power down mode http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52840.ps/qspi.html?cp=2_0_0_5_18_6#deep_power_mode. In addition you should check that CS is deselected.

RE: nRF52840 QSPI XIP and standby

changjo — Mon, 16 Apr 2018 22:06:56 GMT

I have tested out the workaround but this does not fix the issue I have. The anomaly 122 workaround is for un-initializing the qspi chip. Whereas the situation I am referring is in between xip operations, I would like the qspi chip to go into standby.

RE: nRF52840 QSPI XIP and standby

run_ar — Mon, 16 Apr 2018 11:50:24 GMT

Did you implemented the workaround mentioned in anomaly 122?