Basic CPU core sleep

Joe,

what part are you using?

Regards,

Abhishek

Sorry, I am using the TMS570 part. 

I also tried the following assembly language:

    LDR  R0, =0
    MCR  p15, 0, R0, c7, c0, 4
    WFI

I did a special read of internal register to see if the part supported the WFI:

    MRC p15, 0, R0, c0, c1, 6 ; Read Memory Model Feature Register 2.

It does.

Joe,

are you making sure that there are no pending interrupts, as this may be preventing the clock from going off.

Yes,

I added code to readback pending interrupts and there were none.

So, you must be puzzled to then!

Thanks,

Joe

Hi Joe,

The CPU sleep (WFI) is separate from the device level clocking sleep modes.  In most cases, shutting down GCLK will not significantly reduce CPU current consumption further as the R4F has fairly efficient clock gating.  To simplify debugging of your code, I would suggest that you focus only on the WFI first, and then look to manipulating the clocks to further reduce the current consumption.

When you issue the WFI command, there are only three items which can wake the CPU (per ARM Cortex R4F TRM r1p3, P. 268):

• reset
• an interrupt
• a debug access

You have confirmed that no interrupts are pending.  Can you please confirm that you do not have the debugger connected when you are performing your tests?

Regards,

Karl

Karl,

I have performed the test with my code containing the WFI running out of flash without the debugger connected.  It still does not sleep.  There are also no interrupts pending that I can tell.

Thanks,

Joe