Microsoft Word - Digital Logic Design v_4_6a

1.2. Digital vs. Analog

Natural forces and signals are all analog (or continuous) which means we hear, see and change items in
a continuous manner. On the other hand, our digital technology (also called non-continuous or 2-value
discrete) more effectively allows us to process and communicate more effectively. This leads us to
design systems that fit the following block diagram architecture:

 Why convert analog data to digital data?

We have the information we need (on-off, timing)
 Above a certain level is on, high, 1-state or true.
 Below a certain level is off, low, 0-state or False.

Note: We have introduced a discontinuity when a signal goes from 1 to 0 or 0 to 1. This

means we cannot say what the exact value is at the time of transition.

 Reduces complexity of signals and the solutions to work with the signal.

 To deal with a digital signal we need to deal with binary algebra.

 To deal with an analog signal we need to deal with calculus to approximate.

 Positive vs. Negative logic

 Positive Logic Convention (Default  easier for humans to understand)

• H, (V > Vmax) is 1-state or True


• L, (V < Vmin) is 0-state or False
   Negative Logic Convention (1 is L and 0 is H)


• H, (V > Vmax) is 0-state or False


• L, (V < Vmin) is 1-state or True

Real World

Signal

Analog to

Digital

Convertor

(Audio, ..)

Process/

Store/

Communicate

Convertor

Digital to

Analog

Convertor

(Audio, ..)

Real World

Signal

Example: Music Microphone Memory Chip Speaker Music