Vccd pins must be shorted using a short trace and the de-couping capacitor of 1uF is recommend for those pins. The specs guaranteed in the datasheet are met when the design guidelines are followed. Additionally we recommend you to place smaller values of decoupling capacitors closer to the controller as they can respond to high frequency current requirements faster. You can also use place smaller capacitors in parallel with larger capacitors to increase the frequency response range.
The following documents can be helpful for EMC/EMI issues.