Can someone explain to me what a "latched driver" is?
Is it similar to a shift register? I have some on LED matrix that I am trying to control with the arduino.
Here's the specific IC that I would like to interface with:
UCN 5801R
Heres my original thread:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1278272737/6
I figured I should first find out what kind of ICs I am dealing with so I made a new thread.
A latched driver is a chip whose outputs will "remember" the states of the inputs at the time you "latched" data into them by manipulating some sort of clock signal.
A shift register is sort-of a special case of a latched driver, where the inputs can be loaded serially, but the UCN5801 is a parallel-loaded latch, which means that you have to provide 8 arduino outputs to drive its inputs, plus an additional arduino output to drive the "strobe" signal.
Because the outputs are latched, you can share the 8 "data" outputs between multiple UCN5801s if you just have an additional strobe for each chip. So 16 bits of output would need only 10 arduino pins, 24 bits would need 11, and so on.
Wonderful explanation! This is a big step toward controlling my matrix. Thank you for your help 
I'm a beginner at this, and the way I think about it is as a serial to parallel converter. Your bits enter in one by one (serial), and are released simultaneously (parallel) when the latch is triggered. I'm dumb.