The main difference between this device and the L6506 is that it takes a clock input from the microcontroller rather than the four phase inputs. The translator block is a state machine that generates the phases for full step or half step drive for a stepper. The current control works in the same way as the L6506. The phase and enable outputs from the translator are combined with the PWM by the logic block. The control input selects either fast decay, feeding the PWM on to the enable pins, or slow decay, feeding the PWM onto the phase pins.