Computer Science 220
Assembly Language & Computer Architecture

Fall 2011, Siena College

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Agenda

• Announcements
  • opinions about textbooks for OS.
• Lab 110: submit the in-lab sheets any time before your next lab meeting; Logisim circuits by email
• Unix Tip of the day: alias
• Lecture assignment 0x0e recap
• Adding Circuits
  • Ripple carry adders
  • Subtractors
  • More efficient adders
• Sequential circuits
  • edge detection
  • clocks
• Latches and Flip-flops
  • S-R Latch
  • Clocked S-R Latch
  • Clocked S-R Flip-Flop
  • D-type Flip-flop
  • JK-type Flip-flop
  • T-type Flip-flop

Lecture Assignment 0x0f

Due at the start of class, Tuesday, November 1.

Please submit answers to these questions either as a hard copy (typeset or handwritten are OK) or by email to jteresco AT siena.edu by the start of class. Please use a clear subject line when submitting by email (e.g., CS 220 Lecture Assignment 0x0f, Joe Student). We will discuss these questions at the start of class, so no late submissions are accepted.

1. Consider a 2-bit ripple-carry adder and a direct implementation of a 2-bit adder using sum-of-products circuits (3 functions of 5 inputs). You need not construct the actual circuits, but discuss the relative costs in terms of gate count and gate delay. How do you think these change as the number of bits increases? (4 points)
2. Draw a circuit diagram for a 3-bit ripple-carry adder/subtractor using basic logic gates rather than the abstractions we have used for half adders and full adders. You may use inverters, AND, OR, NAND, NOR, and XOR gates. (6 points)

Examples

• logisim