reversing a micro motor by reversing two pins - one Source and one sink?
**Required:**  

Drive micro-motor directly from two processor pins.   

 - Pin 1 high / Pin 2 low for one direction.  
 - Pin 1 low / Pin 2 high for other direction.**


This is not a very good idea if it can be avoided but yes, you can operate a motor that way,  providing that the motor current is low enough to meet the pin current ratings. It would have to be a very small motor to achieve this.

Take careful note of the current versus voltage drive capabilities of the processor concerned. While a pin may be shown as being able to source or sing 5 or 10 or 20 mA, this is accompanied by a voltage rise for a sink and voltage drop for a source, so at higher currents lower voltages will be available. 

A danger is that motor noise may affect the processor.
Placing a small capacitor across the motor will help, and driving the motor through a small resistor from each pin will also help keep noise away from the processor. But depending on the motor used this may not be enough.
The series resistors will drop some voltage and so are limited in maximum allowable size.
The parallel capacitor will slow the direction transition - the larger the capacitor the slower the change.

Using drivers or "buffers" which are higher current rated would allow a larger motor to be driven and would help isolate the processor from the motor noise. 

Ask further if any idea here sounds useful.



Added: Had a discussion with Gerben (below).
I'd avoided mentioning "catch diodes" but this is an add on that can help.
From each pin add a small Schottky diode* from pin to Vcc and pin to ground so that all 4 diodes are reverse biased.
(ie Cathode goes to Vcc = line on diode on upper diodes.
Anode goes to ground on "lower" diodes. )
These diodes are usually non conducting. If motor operation or switching causes spikes that rise above Vcc or below ground these diodes will conduct (slightly) before  the internal protection diodes do. This is not ideal but can help.
As Gerben notes, when reversing the motor, driving BOTH pins to ground until the motor has stopped and then applying reversing polarity can help. Also driving both high will do the same. There are pros and cons with either method.   


eg BAT54 surface mount,   BAT48 through hole, 1N581x  or similar.