The answer is that there are actually some states halfway between the full step positions that the motor can easily be driven to. These positions are obtained by simply turning off the current in one coil before turning it on in the opposite direction. Here, state 1, 3, 5, and 7 are the same as the full step sequence shown before. States 2, 4, 6, and 8 have current in one winding and no current in the other. Since these positions are halfway between the full step positions, they are referred to as half steps. The drive sequence to operate the motor in half step then has 8 states per electrical cycle. The advantage is that the number of steps per revolution can easily be double, so a 1.8° per step motor now gives 0.9° of resolution.