Trouble with stop3 exit on QG8 batt application

[sauz22]

We are developing a prototype using the QG8 microcontroller along a matrix keyboard, but we can not enter the stop3 mode, for low power consumption  so we are asking for advice to achieve our goal. thanks 

[paul]

I had the same problem and it turned out to be a combination of several things.

I had to disable the BDM bit in SOPT1 and run the circuit with the BDM disconnected.

I had a floating input and an output trying to pullup a load.

I also had to do the following:

       ldhx     #SPMSC1
       lda     0,x
       and     #%11110111      ;clr LVDSE bit
       sta     0,x
  
      bclr     ICSC1_IREFSTEN,ICSC1   ;disable clk in stop mode

Disable the low voltage sense and disable the internal clock.

In my case, I was still drawing approx 70 uA... which was not acceptable. It turned out that I was using the internal IRQ pin pullup and had a 1Hz square wave waking up the processor every second via the IRQ pin..... I disabled the internal pullup and used an external  470K pullup instead. The circuit works great and power consumption of approx 3 uA that includes also powering the RTC, a couple other ICs.

Hope this helps you or anyone else out... That took a couple days of scratching my head to resolve.

Paul

[RockyRoad]

Is your problem really entry or exit from stop3?

If entry, is the issue that you are not seeing low current? A possible reason is that you are using a BDM debugger and with BDM active you won't get the low stop current because BDM is running. Or you could have some floating inputs that are still causing high stop current.

If you are truly not getting into stop3, did you configure the STOPE bit in SOPT1? Also remember that STOPE is a write-once bit, so you have to configure all the bits in SOPT1 with one write.

You could also be getting into stop3, but immediately exiting because there is an interrupt pending. This could look like you're not getting in.

If these guesses don't help, post some details about your issue and I'll try to help.

- Rocky