LPM4 problem

Dave14551

Other Parts Discussed in Thread: MSP430F2471

Hi,

I'm haing a problem with Low Power Mode on an MSP430F2471 and was wondering if somebody could help me with it? The problem is that when I go into low power mode the external 12MHz resonator (which I have connected to XT2, and is used to source MCLK and SMCLK) stays on and so the processor consumes allot of power.

If I turn off XT2 before entering LPM4 (but setting XT2OFF flag) the resonator turns off once I enter low power mode. However when I trigger an interrupt the resonator starts up again but no code is executed. It's as if the system is stuck in some "inbetween mode".

When I try to debug it with the debugger the breakpoint at the start of the ISR that took the system out of low power mode does not get hit and if I press pause I get a message saying could not reset target. Has anyone seen something like this before.

Thanks,

Dave

over 16 years ago

0 old_cow_yellow over 16 years ago

Guru 58965 points

The TI "fail-safe" feature is failing you and the "FET Debugger" is bugging you.

If you use XT2 to source MCLK and SMCLK, you should not set XT2OFF.

If you use LPM, you cannot debug around that part of the code.

0 Dave14551 over 16 years ago in reply to old_cow_yellow

Prodigy 245 points

Hi old_cow_yellow,

Thanks for your response, I wasn't aware about the debugger issue, thanks for that.

Would you have any idea why the XT2 resonator is still on while in Low power mode 4 if I do not set XT2OFF? I thought that once the processor went into this mode it disabled all the clocks and this would turn off XT2?

Dave

0 old_cow_yellow over 16 years ago in reply to Dave14551

Guru 58965 points

You need to read the fine prints about the OSCOFF bit in SR register.

0 Dave14551 over 16 years ago in reply to old_cow_yellow

Prodigy 245 points

O I see,

So really the only way to turn off XT2 and LFXT1 during LPM is to switch MCLK and SMCLK to either the DCO or the VLOCLK.

Thanks for your help,

Dave

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LPM4 problem