Flyback diode to prevent back voltage

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So I am currently using TB6612FNG motor driver (see https://www.sparkfun.com/products/9457) to drive two dc motors. Now I wanted to connect a flyback diode (1n4001) to prevent any potential damage to the motor driver that may occur from the back voltage of the dc motors after I terminate the power. Normally, if the motor was only running in a single direction it wouldn't be an issue, as I can easily hook up the diode in parallel across the motor. Since I'm controlling a motor that can spin in either direction, I'm not entirely sure how to connect the diodes as to prevent back voltage to the driver. Thanks.
 
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So I was looking at this schematic for the diodes http://cdn.instructables.com/FYE/O8QZ/H21CGJYJ/FYEO8QZH21CGJYJ.LARGE.jpg and I'm trying to understand why are diodes connected from ground to motor terminals ??
 
You can put in 2 diodes per motor terminal so the voltage won't go much below ground or above the power supply. That will protect the attached components (assuming they can handle the slight rise above the supply or fall below ground). If there is a problem with that, you can use schottky diodes (check leakage and reverse voltage capability).
 
What if I hooked up only 4 diodes and did not hook up the 4 diodes connected to ground? (Based on the schematic given above).
 
Then the voltage could spike below ground and damage the driver.