Microsoft Word - Digital Logic Design v_4_6a

 A wired-OR can be created by using the DeMorgan’s Theorem: A+B=A.B

 Example - Using Wired-OR to implement F= AB.. C+AB.. C+D with the Signal List
SL: F, A, B, C, D.
.

 Tri-State, 3-State or High impendence-State Output

An input is used to decide if the output is being driven (enabled).

 If the output is enabled, then it behaves like a normal 2-state device

 If the output is disabled, then the output has high impedance (referred to as “hi-Z”).

 74LS125 is a good example:

Input Output

OE A F

1 X Z

0 1 1

0 0 0

Notes:

Indicates a 3-state output

A F

OE

A B C D

Wired-AND

F

A

B

A+B

Wired-OR

Vcc Vcc