文档介绍：Digital concept and Number system
Chapter 1
Digital system
Digital system:
entity
can process, transfer and store any kind of digital signals
posed of individual digital logic circuits which are designed to perform specified function
physical signal (transformation rule)
Digital signal: discrete quantities
Analog signal: continuous quantities
The difference between analog and digital lies in the method of Encoding information
Digital logic circuit
A circuit used to process digital signal.
All function of the circuit are realized by performing Boolean calculation or Boolean judgment.
It operates on numbers that represent some real logical or arithmetic function.
Digital logic circuit
E = A+B
A4A3A2A1 B4B3B2B1
F4 F3 F2 F1
CO
CI
E
B
A
“ 0”
Digital logic circuit
The basic logic functional units that perform primitive logic functions are called gates.
&
A
F
B
C
&
&
+
F(A,B,C)=AB+AB’C’+A’BC
Digital logic circuit
The work signal is restricted to two binary values 0, 1.
0 and 1 are logic value.
They can represent the voltage level of a circuit , 1 is high level and 0 is low.
They also can represent the two states of transistors, conduct is defined as logic 1 and cutoff is logic 0
Digital logic circuit
Studying the digital circuit , we are concerned with the relationship between the input and output, the function it provide, not the internal detail.
Digital integrated circuits, constructed from ponents, are designed to perform specified logic functions.
Simple integrated circuits contain a few logic gates is called small-scale integration (SSI contains 0 to 9 gates)
Medium-scale integration (MSI contains 10 to 99 gates)
Large-scale integration (LSI contains 100 or more gates)
Very large–scale integration (VLSI does not have a gate count but is usually thought of as more than 1000 gates)
Digital logic circuit
Components level
First IC level (SSI)
Level four
Level three
Level five
ponents, . transistors, diodes, resisto