# School Logic Gates Task

Discussion in 'Homework Help' started by TJAbundo, Jun 7, 2014.

1. ### TJAbundo Thread Starter New Member

Jun 7, 2014
1
0
My friends and i were tasked to complete this, we got the most part done, but we are stuck with in this part.

a) Modify the 8 bit adder so that is has some extra outputs. In addition to the Carry flag,
it should have a Zero flag, a Negative flag and an Overflow flag. Zero indicates if
the result of the operation is zero and Negative indicates of the result is negative,
when using a twos complement format. The Overflow flag is trickier; it demonstrates
if a twos complement number has become too large and changed sign as a result.
For example, if you add 127 and 3, you get -126 and if you add -120 and -30, you get
106!! The overflow flag output should be set to indicate when this has happened (HINT:
overflow can only occur when the two numbers being added have the same sign)
b) Modify the subtractor circuit so that it also has these extra outputs (this should be
relatively simple as you can reuse the outputs from your new, modified 8 bit adder)
c) Make a 4 bit multiplier by reusing the 8 bit adder and/or the 4 bit CLA adder
components. It should be able to multiply two 4 bit numbers and produce an 8 bit result.
You should assume that the four bit numbers are both positive for this purpose.

Please Help us

2. ### crutschow Expert

Mar 14, 2008
13,462
3,353
So what have you done so far?

Do you understand adder and subtractor circuits?

What type of help do you need? We don't do homework but we can help with questions, of which you have posted none.