Just define a HSCDEF channel and by default the channel will count up if phase B is held at OFF.
E.g. for FMD88-10, input #3 and #4 forms a quadrature channel. By default without forcing into enhanced quadrature, the HSC will count up when input #4 is OFF and pulses coming into input #3.
Alternatively, if input #3 is held at OFF and pulses come into input #4 then HSCPV will decrement.