As far as I know, motor control drivers are controlled by incremental way, where you use two pins - one for the direction and the other for steps. However, the steps should be very very short (about few uS?). I have no idea, if it is possible to force Pokeys to control it. On the other way, step motor can be controlled by putting voltage on one or the other pair of connectors. Maybe it would be better to use arduino as intermediate controller for AX1201728SG, which would read the analogue value of request from PoKeys and transform it to the digital form requested by the chip?