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Basic ElectronicsNinth Edition
Basic ElectronicsNinth Edition
©2002 The McGraw-Hill Companies
GrobSchultz
GrobSchultz
Basic ElectronicsNinth Edition
Basic ElectronicsNinth Edition
©2003 The McGraw-Hill Companies
31CHAPTER
Digital Electronics
Topics Covered in Chapter 31
Binary and Decimal Numbers
Decimal to Binary Conversion
Hexadecimal Numbers
Binary Coded Decimal System
The ASCII Code
Logic Gates, Symbols, and Truth Tables
Boolean Algebra
DeMorgan's Theorem
Treating Unused Inputs
TTL and CMOS Circuits
Active HIGH/Active LOW Terminology
Topics Covered in Chapter 31(continued)
Topics Covered in Chapter 31(continued)
Combinational Logic Circuits
Binary Adders
Flip-Flops, Counters, and Registers
New Logic Symbols
Troubleshooting Digital Circuits
Number Systems• Decimal
Base 10; digits are 0 through 9 Most commonly used by humans
• Binary Base 2; digits are 0 and 1 Most commonly used by computers
• Hexadecimal Base 16; digits are 0 through F
• BCD Binary Coded Decimal
Decimal Binary Hex
0 0 0
1 1 1
2 10 2
3 11 3
4 100 4
5 101 5
6 110 6
7 111 7
8 1000 8
9 1001 9
10 1010 A
11 1011 B
12 1100 C
13 1101 D
14 1110 E
15 1111 F
Decimal (base 10)13410 = 4 x1 + 3x10 + 1x100 = 13410
Different Base Numbers
Binary (base 2)100001102 = 0x1 + 1x2 + 1x4
+0x8 + 0x16 + 0x32+0x64 + 1 x 128 = 13410
Hex (base 16)8616 = 6x1 + 8x16 = 13410
Logic Inverter
• A logic inverter switches the state of its input. Changes 0 to 1
Changes 1 to 0
• Logic inverters can invert the outputs of other logic gates. Change an AND gate to a NAND gate Change an OR gate to a NOR gate Change an XOR gate to an XNOR gate
A10
B01AB
XOR/XNOR Logic Functions
XOR function
XNOR function
B0011
C0101
A0110
B0011
C0101
A1001
ABC
ABC
A = B+C
A = B+C
Combinational Logic Circuits
A B C X
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1
A
BC
X
X = A(B + C)
X = ABC + ABC + ABC + ABC
A B C X
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1
Truth Table Boolean Expression Simplify
X = BC(A + A) + AB(C + C)
X = BC + AB
Factor:
1
{
1{
Flip-Flop Circuits
• Flip-flop circuits are digital devices that hold a 0 or 1 output until some event triggers them to the opposite output.
• They are commonly used for storing digital data on a temporary basis.
Major Types of Flip-Flop Circuits
• Set/reset (SR) flip-flops.
Q
Q
S
R
Q
Q
D
CLK
Q
Q
J
K
• J-K flip flops.
• D-type flip-flops.
Q
Q
J
Negative-Edge Triggered JK Flip-Flop
Q
CLK
J
Time
CLKK
K
Mode J K Q
Inhibit 0 0 Q
Set 1 0 1
Reset 0 1 0
Toggle 1 1 Q
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