Let me confirm Output Buffer Impedance and Drive Strength Field with i.MX6UL.
I think there are some wrong description about Output Buffer Impedance and Drive Strength Field.
Here is a table which shows the relationship between Output Buffer Impedance and DSE in IMX6ULCEC.
On the other hand, here is a table which shows the setting of DSE and the impedance value in IMX6ULRM.
Comparing the above, I think the table 33 of IMX6ULCEC is for OVDD = 3.3V and table 34 is for OVDD = 1.8V.
Am I correct ?