View Full Version : XMC1000 DCO calibration

Oct 10th, 2013, 03:36 AM
Hello All,

the XMC1000 reference manuals describe the ANAOFFSET register to have four bits with a numerical a range of 0..8, where a "DCO_ADJR" bit should set the adjustment range. But there is no description of "DCO_ADJR" in the whole reference manual.

The DCO_ADJL_RT and DCO_ADJL_HT description says there are 5 bits to be transferred to ANAOFFSET.ADJL_OFFSET, but ADJL_OFFSET is only four bits wide. A documentation error?

Besides this, I don't understand the calibration at all. Which values have to be written to ANAOFFSET.ADJL_OFFSET, shall I interpolate something? To which temperatures are DCO_ADJL_RT and DCO_ADJL_HT referenced?

More questions than answers, IMO.

BTW: The data sheet states a frequency deviation of more than +-3% where ADJL_OFFSET can trim only +-2,8% even with DCO_ADJR set, so the trim option seems to be a bit limited.


Oct 17th, 2013, 08:22 PM
Hi Oliver,

The 5 bit value for DCO_ADJL_RT and DCO_ADJL_HT is hard coded into the device during production.
This is the parameter use to calculate the offset value.
However, currently the formula to calculate the offset value is not available yet.
Once the formula is available, user can calculate the offset value and set the offset value from ANAOFFSET.ADJL_OFFSET.
The result from the offset calculation will be in term of 'Steps' value, and this can be calibrate from -4 to 4 as stated in the ANAOFFSET.ADJL_OFFSET.
As for the present of 'DCO_ADJR' in the documentation, it is due to the documentation error.
I hope I have clear your doubt.

Oct 18th, 2013, 01:50 AM
Hi Jackson,

thanks for the reply.

When will a suitable documentation be available?

This means, a conclusive description of the ANAOFFSET register, a formula for the correction value, and a specification of the remaining tolerance of the "temperature compensated" DCO?

I would like to use the XMC1x00 for a new design, but I can't use it with 3% oscillator tolerance.