hi friends i have problem with logic works i need Logarithm circuit with "logic works" can someone help me???? plzzzzzzzz

First, what kind of logarithm circuit are you talking about? Analog, digital, ...? This is not the Homework Done For You forum. You need to show YOUR best attempt to solve YOUR homework problem. We will then help guide you along the path to the solution if we can.

i exactly dont know what kind ? analog or digital? but i not one kind electric circuit diagram can be design with logic work like this : http://t0.gstatic.com/images?q=tbn:ANd9GcSHOVeCKma5-JakuSBwuYzJ0m3N7vFPyE-Qq4Lm494X1M5c0IMo but i say i become dizzy ( help me plzzzzzzz

Again, how are the values A and B represented? Unsigned integers? Two-complement? IEEE Floating point? What, exactly, is the assignment?

Okay. So focus on taking the base-2 logarithm of a two's complement number. What representation is the output supposed to be in?

"seven segment" is not a representation format. A representation format is something like "unsigned binary", "twos-complement", "IEEE-754 single-precision floating point", "fixed point".

Okay. So what should the output of your circuit be if the input is 5? What should be displayed? What if the input is -12?

I don't understand what you are saying here. I suspect it is just a language barrier problem, so try rephrasing. You said that if you have an input value of 5 that the output should show error. So in response to that I have two questions: Why should the base-2 logarithm of 5 produce an error? How will you show an error on your 7-segment displays? In addition, I asked you to describe what input values (at least give an example or two) should not produce an error and what the output values should then be.