PWM control stuff

Your common H bridge driver consists of 4 switching parts, organized in two halfs. 
    Each half can switch its motor wire to positive or negitive.






A high
 A low
 B high
 B low
 Motor
off
 off
 off off off (coast)
off on
 on off forward
on off off on reverse
on off on off brake
off on off on brake
off on off off off (coast)
on off off off off (coast)
off off on off off (coast)
off off off on off (coast)


Ways an H bridge is operated to control the speed and direction of a motor

There are a few different ways people do this

A) keep one side either high or low, if the other side is off, the motor will coast, if its high, the motor will go one direction, low pulses will make it