I'm trying to understand what happens at various points in a circuit during drive-coast operation (and also drive-brake, but haven't got there yet). Imagine Q1 and Q3 are on, and Q2 and Q4 are off, such that current flows left to right in the motor. If Q1 and Q3 are now shut off, point B would jump to 10V + Vf (forward voltage of diode) and A would jump down to -Vf. Current would flow from point B through D4 into positive side of the power supply. Current would also flow from ground, through D2, to point A.
Once some of the energy has dissipated point B would be just below 10V + Vf, and so current would no longer flow through D4, and similar situation with D, because the diode is no longer in the forward bias region. What happens after this? Does B just remain at that particular voltage? At this instance let's say the motor is still spinning freely (with only little deceleration due to friction), close to what is was when being driven. Would the back EMF cause A to increase and B to decrease? Basically I'm confused on what the voltages at points A and B are at various time points after Q1 and Q3 have been shut off.