HW6-Solution

HW6-Solution - 800 ps: 150 ps borrowed through L1, 330 ps...

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EL 5473 Introduction to VLSI Design Homework Assignment 6 Due beginning of Class April 13, 2010 1. (Problem 7.8 in text) Consider a flip-flop built from a pair of transparent latches using non- overlapping clocks. Express the setup time, hold time, and clock-to-Q delay of the flip-flop in terms of the latch timing parameters and t non-overlap . Answer: t setup-flop = t setup-latch + t non-overlap ; t hold-flop = t hold - t non-overlap ; t pcq-flop = t pcq . 2. (Problem 7.9 in text) For the path in the figure below, determine which latches borrow time and if any setup time violations occur. Repeat for cycle times of 1200, 1000, and 800 ps. Assume there is zero clock skew and that the latch delays are accounted for in the propagation delay ’s. a. 1 = 550 ps; 2 = 580 ps; 3 = 450 ps; 4 = 200 ps b. 1 = 300 ps; 2 = 600 ps; 3 = 400 ps; 4 = 550 ps Answer: (a) 1200 ps: no latches borrow time, no setup violations. 1000 ps: 50 ps borrowed through L1, 130 ps through L2, 80 ps through L3.
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Unformatted text preview: 800 ps: 150 ps borrowed through L1, 330 ps borrowed through L2, L3 misses setup time. (b) 1200 ps: no latches borrow time, no setup violations. 1000 ps: 100 ps borrowed through L2, 50 ps through L4. 800 ps: 200 ps borrowed through L2, 200 ps borrowed through L3, 350 ps borrowed through L4, 250 ps borrowed through L1, L2 then misses setup time. 3. (Problem 10.1 in text) Design an 8-bit adder. The inputs may drive no more than 30 of transistor width and the output must drive a 20/10 inverter. Simulate the adder and determine its delay. Simulation. 4. (Problem 11.3 in text) Sketch designs for a 6:64 decoder with and without pre-decoding. Comment on the pros and cons of pre-decoding. Answer: The design with pre-decoding uses 16 3-input NANDs while the design without uses 128. Both designs have the same path effort. Hence, the layout of the pre-decoded design tends to be more convenient....
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HW6-Solution - 800 ps: 150 ps borrowed through L1, 330 ps...

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