What is Logic in a circuit?

• ●  Adds decision making to a circuit

• ●  Simple to complex computation

• ●  Below the surface they are a clever combination of transistors and op amps

Different ICs serve unique functions

• ●  We have already encountered NOT gates (Inverter for our oscillator)

• ●  There are many other ICs with different sets of logic functions and combinations of

  logic

Ins and Outs

• ●  For the most part logic will output a high or low (usually Vcc or GND) depending on it’s inputs

• ●  Something called a “Truth Table” shows how logic gates react to different high or low inputs

Transistor Logic

• ●  Remembering from our transistor talks

• ●  The base of the transistor acts like a

  switch

• ●  For these transistors signal only

  passes through when the base sees a

  voltage

• ●  So the only way Out gets anything is

  when both transistors have voltage at their bases

Logic Combinations

• ●  Beginning stages of memory

• ●  Flip Flops

• ●  Combine basic logic to do more

  complicated tasks

• ●  This is how we can use hardware to

  make decisions

A chip that is a counter

• ●  We’ll be basing our sequencer on a 4017 decade counter

• ●  Takes a clock input and counts up to ten

• ●  Reset (MR) will repeat the count over and over again