Computer Science 237 Computer Organization Williams College Fall 2005

Announcements

• Computer Science colloquium today, 2:30 PM, TCL 206, Computer Science Faculty discuss their research.
• We will meet for labs next week in TCL 216. We'll begin at 1:15, should be done by 2.

Agenda

• Wrapup of Subroutines in Assembly
• Sequential Logic Introduction
  • Recall: combinational circuits implement simple functions
  • LEDs and TEDs. Even combinational life isn't so simple.
  • Sequential circuits implement circuits with history; feedback and non-linearity: difficult things to understand.
  • Simple clocks.
  • Bi-stable circuits. Circuits that have two stable states.
  • latches: circuits that have two stable (remembered) states that may be selected by external control.
    • S-R latch; stores while high (or low)
      • NOR gate version (our preference)
      • Inverted logic NAND gate version (common)

Examples

• strcpy