Hi guys, when i set my address line high it gives an output of 5V does this mean that it is active high? and the definition of active low would mean that it would goto -5V or would it have a transition from 5V to 0V thx.

 

Logic levels are generally 0 volts for low, and +5 for high.

In the case of your address line, the logic high simply means that that bit is true.

Let me point you at a previous discussion about the subject - http://forum.allaboutcircuits.com/showthread.php?t=10619.

 

thx....so this wouuld mean that if i have binary of 1111 which give 5v for all of them and now i found out my devices are active low i would need to set it to 0 to trigger its output?

 

The one does not follow from the other. A binary value and a logic gate input are not the same thing.

It is possible to apply four high inputs to a quad input NAND gate, which would cause its output to go low. If that output were connected to another gate, say the reset input of a 7474 flip flop, then that active low reset input would be satisfied, and the flip flop would go to the reset state.