The skew granularity available with RoboClock is dependent on the part (CY7B993V or CY7B994V) employed, the FS setting, and the operating frequency of the VCO, fNOM.
The output skew is programmed through the Skew Function Select Pins, [1:4]F1, [1:4]F0 and FBF0. The RoboClockII skew functionality is dictated in Table 5.
The time unit (tU) calculation is illustrated in Table 1. The maximum skew granularity is available when a CY7B993V is operating in the FS=LOW range with an fNOM=12MHz. In this instance the tU is1.3ns. Configure the feedback bank for -8tU (-10.4ns) and configure one of the other banks for 8tU and the total skew appearing on the bank configured for 8tU is 10.4 - (-10.4)ns = 20.8ns.
The minimum skew is available when a 994 is operating with an fNOM of 200MHz. The tU in this instance will be 625ps.