# kiến trúc máy tính dạng thanh tin figs 3 the digital logic level sinhvienzone com

3
THE DIGITAL LOGIC LEVEL

1

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+VCC
+VCC
+VCC
Vout
V1

Collector

Vout

Vout

Vin

V2

V1

V2

Emitter

Base
(a)

(b)

(c)

Figure 3-1. (a) A transistor inverter. (b) A NAND gate. (c) A NOR gate.

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NOT
A

X

A

NAND
X

B
A
0
1

X

1
0

(a)

NOR

A

X

B
A
0
0
1
1

B
0
1
0
1
(b)

X
1
1
1
0

AND

A

X

B
A
0
0
1
1

B
0
1
0
1
(c)

X
1
0
0
0

OR

A

X

B
A
0
0
1
1

B
0
1
0
1

X
0
0
0
1

(d)

A
0
0
1
1

B
0
1
0
1

X
0
1
1
1

(e)

Figure 3-2. The symbols and functional behavior for the five basic gates.

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A B C

A B C

A
1
A
4

5

B

ABC

ABC

2
A
0
0
0
0
1
1
1
1

B
0
0
1
1
0
0
1
1

C
0
1
0
1
0
1
0
1

(a)

M
0
0
0
1
0
1
1
1

8

B
6
ABC
C
3
C
7

ABC

(b)

Figure 3-3. (a) The truth table for the majority function of
three variables. (b) A circuit for (a).

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M

A

A

A

A
(a)

A
A

AB

A+B

B
B

A
AB

A

A+B

B
B
(b)

(c)

Figure 3-4. Construction of (a) NOT, (b) AND, and (c) OR
gates using only NAND gates or only NOR gates.

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AB

A
B

AB + AC

A

A(B + C)

B
AC

C

B+C

C

A

B

C

AB

AC

AB + AC

A

B

C

A

B+C

A(B + C)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

1

0

1

0

0

1

0

0

0

0

0

1

0

0

1

0

0

1

1

0

0

0

0

1

1

0

1

0

1

0

0

0

0

0

1

0

0

1

0

0

1

0

1

0

1

1

1

0

1

1

1

1

1

1

0

1

0

1

1

1

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

(a)

(b)

Figure 3-5. Two equivalent functions. (a) AB + AC. (b) A(B + C).

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Name

AND form

OR form

Identity law

1A = A

0+A=A

Null law

0A = 0

1+A=1

Idempotent law

AA = A

A+A=A

Inverse law

AA = 0

A+A=1

Commutative law

AB = BA

A+B=B+A

Associative law

(AB)C = A(BC)

(A + B) + C = A + (B + C)

Distributive law

A + BC = (A + B)(A + C)

A(B + C) = AB + AC

Absorption law

A(A + B) = A

A + AB = A

De Morgan's law

AB = A + B

A + B = AB

Figure 3-6. Some identities of Boolean algebra.

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AB

=

A+B

A+B

(a)

AB

=

(c)

=

AB

(b)

A+B

A+B

=

AB

(d)

Figure 3-7. Alternative symbols for some gates: (a) NAND. (b) NOR.
(c) AND. (d) OR.

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A

A

B

XOR

0

0

0

0

1

1

1

0

1

A

1

1

0

B

B

(a)

(b)

A

A

B

B

A

A

B

B
(c)

(d)

Figure 3-8. (a) The truth table for the XOR function. (b)-(d)
Three circuits for computing it.

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A

B

F

A

B

F

A

B

F

0V

0V

0V

0

0

0

1

1

1

0V

5V

0V

0

1

0

1

0

1

5V

0V

0V

1

0

0

0

1

1

5V

5V

5V

1

1

1

0

0

0

(a)

(b)

(c)

Figure 3-9. (a) Electrical characteristics of a device.
(b) Positive logic. (c) Negative logic.

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VCC
14

13

12

11

10

9

8

1

2

3

4

5

6

7

Notch

GND

Figure 3-10. An SSI chip containing four gates.

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Pin 8

D0
D1
D2
D3
F

D4
D5
D6
D7
A A B B C C

A

B

C

Figure 3-11. An eight-input multiplexer circuit.

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VCC

D0

D0

D1

D1

D2

D2

D3

F

D4

D3

D5

D5

D6

D6

D7

D7

A B C
(a)

F

D4

A B C
(b)

Figure 3-12. (a) An MSI multiplexer.. (b) The same multiplexer wired to compute the majority function.

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D0

D1

A

B

A

D2

A

D3

B

D4

B
C

D5

C
C

D6

D7

Figure 3-13. A 3-to-8 decoder circuit.

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EXCLUSIVE OR gate
A0
B0

A1
B1
A=B
A2
B2

A3
B3
Figure 3-14. A simple 4-bit comparator.

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A

If this fuse is
blown, B is not
an input to AND
gate 1.

B
12 ϫ 2 = 24
input signals

L

24 input lines

0

1

49

0

1
6 outputs
If this fuse is
blown, AND gate
1 is not an input
to OR gate 5.

50 input
lines

5

Figure 3-15. A 12-input, 6-output programmable logic array.
The little squares represent fuses that can be burned out to
determine the function to be computed. The fuses are arranged
in two matrices: the upper one for the AND gates and the lower
one for the OR gates.

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D0

D1

D2

D3

D4

D5

D6

D7

S0

S1

S2

S3

S4

S5

S6

S7

C

Figure 3-16. A 1-bit left/right shifter.

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Exclusive OR gate
A

B

0

0

0

0

0

1

1

0

1

0

1

0

1

1

0

1

Sum Carry
A

Sum

B

Carry

Figure 3-17. (a) Truth table for 1-bit addition. (b) A circuit for a half adder.

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Carry in
Carry
Carry
Sum
in
out

A

B

0

0

0

0

0

0

0

1

1

0

0

1

0

1

0

0

1

1

0

1

1

0

0

1

0

1

0

1

0

1

1

1

0

0

1

1

1

1

1

1

A

Sum

B

Carry out
(a)

(b)

Figure 3-18. (a) Truth table for full adder. (b) Circuit for a full adder.

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Logical unit

Carry in

AB
INVA
A
ENA
B
ENB

A+B

Output

B
Sum

Enable
lines

F0

Full

F1

Decoder

Carry out

Figure 3-19. A 1-bit ALU.

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F1 F0

A7 B7

A6 B6

A5 B5

A4 B4

A3 B3

A2 B2

A1 B1

A0 B0

1-bit
ALU

1-bit
ALU

1-bit
ALU

1-bit
ALU

1-bit
ALU

1-bit
ALU

1-bit
ALU

1-bit
ALU

O7

O6

O5

O4

O3

O2

O1

O0

Carry
in

Carry
out

Figure 3-20. Eight 1-bit ALU slices connected to make an 8bit ALU. The enables and invert signals are not shown for simplicity.

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INC

C1

Delay

C2

(a)

(b)

A
B
C
(c)
Figure 3-21. (a) A clock. (b) The timing diagram for the
clock. (c) Generation of an asymmetric clock.

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S

0

1

Q

S

0

0

Q

1

1
R

0

0
0

0
(a)

Q

R

1

0

Q

A

B

NOR

0

0

1

0

1

0

1

0

0

1

1

0

(b)

(c)

Figure 3-22. (a) NOR latch in state 0. (b) NOR latch in state 1.
(c) Truth table for NOR.

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S
Q
Clock
Q
R
Figure 3-23. A clocked SR latch.

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D
Q

Q

Figure 3-24. A clocked D latch.

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