I am using a ATTiny84 micocontroller to control a L293. When I put my volt meter to each of the output pins on the microcontroller the logic is perfect (it's all slow enough that I can measure it with the volt meter). As soon as the L293 gets plugged in - nothing works. One particular output of the controller drops low for 1 second when a button is pushed - yet there is always 5 volts on the pin when the L293 is plugged in. I am at a complete loss. I have pulled my PCB apart and installed it all on a breadboard and still ahve the same problem. Any ideas on what I can do to trouble shoot this? I assume the ATtin84 can control the L293 (10 ma per output pin, 40 peak but not recommended). Any ideas? I am at a complete loss.

 

Why don't you start by posting a schematic of how you have things wired up.
[eta]
Note that Vcc1/Vss (logic supply voltage; pin 16, pin 20 or pin 28 depending on the package you have) should be >=4.5v, but not more than your ATTiny's supply voltage.

ST Microelectronics indicates that you can use 4.5v to 36v for the logic supply; I believe this is in error. Texas Instruments' L293D has a range of 4.5v to 7v for the logic supply.

 

Do you have a pull down resistor to ground on each of the outputs of the uC?