The maximum hm2 encoder count rate depends on the sample frequency
At the maximum 7I90HD encoder sample frequency of 100 MHz, the built in 3 clock (filter off)
input digital filter means that a quadrature input signal must last at least 30 ns to be detected.
This means an approximate maximum count rate of ~60 MHz. Practical
real world signal integrity considerations limit maximum count rates to about 10 MHz.