In the High Speed SelectIO Wizard rev 3.1 there is no way to change the Delay format.
(The exception to this is for RX Asynchronous interfaces, see (Xilinx Answer 68066))
Note: this Answer Record should not be viewed in isolation. For all other known issues and to see what version of Vivado / High Speed SelectIO Wizard these issues have been resolved in, please refer to (Xilinx Answer 64216)
Xilinx recommends that all Native Mode designs use DELAY_FORMAT = TIME. Therefore, the High Speed SelectIO Wizard only supports DELAY_FORMAT = TIME.
If the user wants to approximate COUNT mode you can use the High Speed SelectIO Wizard code, wait until the built in reset sequence finishes and then pull EN_VTC low.
With EN_VTC = Low the BISC will not run to calibrate for voltage and temperature.
When making changes to the delay line, wait states are required to ensure correct operation. See (Xilinx Answer 67246) for further details.
Note: in older versions of the High Speed SelectIO Wizard also did not have the ability to choose the delay format but if the Delay type FIXED was selected then the format is always TIME. If the Delay type Variable or Var_Load was selected, the format was always COUNT.
This was changed in Vivado 2015.3 so that TIME is always used to follow Xilinx recommendations.