TXRATEDONE would not be expected with the TXRATEMODE (async mode).
All it does is directly change the output
divider with no reset following it.
In sync mode, there is an internal reset that occurs following the change of the output divider.
A follow up GTTXRESET or TXPMARESET by the user would be required if using this in async mode.
(UG482) will be updated with this information in the next release.