[stella] Determining digital state of the 2600 controller ports?

[Stephen Anthony]

First of all, I'm trying to determine exactly how certain ROMs change 
the state of the controller pins wrt AtariVox and EEPROM support.  Does 
anyone know the best way to proceed?

I'd like to hook up some sort of hardware, initiate an action from a 
game, and see how the controller pins are changed as a result.  
Ideally, I'd like to view the data as a stream of 0's and 1's over 
time, all synchronized with each other.  For example, perhaps generate 
seven lines of output, where all the values in some 'column' correspond 
to the state of the pins at that time interval.

Can anyone give some suggestions on how to proceed?  Is the DB9 
controller port on a 2600 compatible with a standard DB9 serial port, 
and if so, could I just hook it up to a computer and read the results?  
If not, what other type of hardware could I use??

Thank in advance for any suggestions,
Steve