## Computer Science 237 |

**Lecture 9: Digital Logic, Combinational Circuits****Date: September 28, 2005**

- We still hate cortland. Hopefully the Unix lab is working out for everyone this week.
- Lab 3 continues. Use
`BRK`and`DEB`directives. If you change your logic for the assembly version, try it out in equivalent C. Come see my C solution for ideas. - No office hours Friday. But I will be around quite a bit on Thursday.

- Introduction to Logic
- Some basic electronics
- The inverter
- Notions of gate delay, signal propagation, loading, transistor/gate budgets.
- The
`NAND`and`NOR`gates; then`AND`and`OR`gates. - Universality of certain gates.
- Laws.
- Identity, commutative, distributive, associative laws.
- Logarithmic gate delay for fan-in of
*n*; linear cost. - deMorgan's: notion of inverted logic

- Question: How do you build an
`XOR`gate? Is it universal? - Generation of all
*combinational*functions (functions that are determined by inputs only).

- Some new, useful functions.
- MUX's and DMUX's.