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Unformatted text preview: ECE 546 ECE 546  VLSI Systems Design VLSI Systems Design ecture ecture 9: Adders 9: Adders Lecture Lecture 19: Adders 19: Adders Fall Fall 2011 2011 W. Rhett Davis W. Rhett Davis NC State University NC State University ith significant material from ith significant material from abaey abaey handrakasan handrakasan and and ikoli ć ikoli ć Slide 1 © W. Rhett Davis NC State University ECE 546 Fall 2011 with significant material from with significant material from Rabaey Rabaey, , Chandrakasan Chandrakasan, and , and Nikoli ć Nikoli ć Announcements Project Milestone #1 Due Thursday HW#8 Due Thursday Slide 2 © W. Rhett Davis NC State University ECE 546 Fall 2011 Summary of Last Lecture What techniques can be used to speed up and duce the power of decoders? reduce the power of decoders? How do you maximize the bitline voltage change V when a DRAM bitcell is accessed? Slide 3 © W. Rhett Davis NC State University ECE 546 Fall 2011 Today’s Lecture dders (11 3) Adders (11.3) » RippleCarry Adder irror Adder » Mirror Adder » Transmission Gate Adder anchester Carry » Manchester Carry » Carry Bypass (Carry Skip) Adder » Carry Select Adder Slide 4 © W. Rhett Davis NC State University ECE 546 Fall 2011 FullAdder A B ull Cout um Cin Full adder Sum “Delete” is sometimes alled “Kill” Slide 5 © W. Rhett Davis NC State University ECE 546 Fall 2011 called Kill The RippleCarry Adder A B A 1 B 1 A 2 B 2 A 3 B 3 FA FA FA FA C i ,0 C o ,0 ( C i ,1 ) C o ,1 C o ,2 C o ,3 S S 1 S 2 S 3 Find t adder in terms of t carry and t sum t adder is O(?) Slide 6 © W. Rhett Davis NC State University ECE 546 Fall 2011 Goal: Make carry chain as fast as possible The Binary Adder A B Cout um Cin Full adder Sum S A B C i = A = B C i ABC i ABC i ABC i + + + C o AB BC i AC i + + = ow can we make this fast? Slide 7 © W. Rhett Davis NC State University ECE 546 Fall 2011 How can we make this fast? Complimentary CMOS Full Adder Reexpress S as a function of C o : i o i C B A C ABC S A B V DD V DD C i B A B A C i A B V DD C i A X A B B V D C i C i S DD A B A C i B C o Slide 8 © W. Rhett Davis NC State University ECE 546 Fall 2011 28 Transistors Can we do better? Today’s Lecture dders (11 3)...
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This note was uploaded on 01/26/2012 for the course EE 546 taught by Professor Whett during the Spring '11 term at N.C. State.
 Spring '11
 Whett

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