COMPUTER ORGANISATION

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COMPUTER ORGANISATION (CS - 46)
Sri. RAVISH ARADHYA H. V., Assistant
Professor, R.V.C.E., Bangalore-560 059. e-mail
ravish_aradhya_rvce_at_yahoo.co.in
H. V. RAVISH ARADHYA., R.V.C.E.
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Chapter-5ARITHMETIC CIRCUITS. Adder/Subtractor,
Multiplier Circuits.
H. V. RAVISH ARADHYA., R.V.C.E.
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Adder/ Subtractor
1
H. V. RAVISH ARADHYA., R.V.C.E.
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Adder/ Subtractor
Adder

• control S 0 -- adder.
• 84 X 1010100
• 67 Y 1000011
• 151 10010111

H. V. RAVISH ARADHYA., R.V.C.E.
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Adder/ Subtractor
Subtractor

• control S 1 -- subtractor.
• 84 X 1010100
• - 67 Y 1000011
• 17

• controlling inputs -- all AL operations.

H. V. RAVISH ARADHYA., R.V.C.E.
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Adder/ Subtractor
With s 0, Xi Ai Yi Bi Ci 0 With s 1,
Xi Ai Yi Bi Ci 1
H. V. RAVISH ARADHYA., R.V.C.E.
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Adder/ Subtractor
Function Table
combinational ckt With s 0, Xi Ai Yi
Bi Ci 0 With s 1, Xi Ai Yi Bi Ci 1

H. V. RAVISH ARADHYA., R.V.C.E.
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Adder/ Sub-tractor

• The design equations (Controlled inverter) for
  an adder or a subtractor are as below

Y1
Y0
Xn-1
X1
X0
An-1 - - - A1 A0
Bn-1 - - - B1 B0
Cn
Fn
F1
F0
H. V. RAVISH ARADHYA., R.V.C.E.
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Binary Multiplier

• Unsigned number multiplication
• two n-bit numbers 2n-bit result
• combinational array may be used
• multiplier bit decides
• whether multiplicand to be
• added to incoming PP
• or shift diagonally

H. V. RAVISH ARADHYA., R.V.C.E.
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Array Multiplier
H. V. RAVISH ARADHYA., R.V.C.E.
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Binary Multiplier

• FA is used as core block.
• q i decides m j to be added or shifted
  diagonally
• too much delay.

H. V. RAVISH ARADHYA., R.V.C.E.
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Binary Multiplier
P7, P6, P5,,P0 product
H. V. RAVISH ARADHYA., R.V.C.E.
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Array Multiplier
H. V. RAVISH ARADHYA., R.V.C.E.
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4 X 3 Multiplier
Prod 7 bits Need 12 AND gates 2-4bit
adders A2 A1 A0 X B3B2B1B0
H. V. RAVISH ARADHYA., R.V.C.E.
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Array Multiplier
Array Multiplier has too much delay. has
too much hard ware no precise control
sequential circuits can be used instructions
can be built
H. V. RAVISH ARADHYA., R.V.C.E.
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Sequential Multiplier
a
H. V. RAVISH ARADHYA., R.V.C.E.
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Flow Chart
H. V. RAVISH ARADHYA., R.V.C.E.
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Shift Add Multiplication
H. V. RAVISH ARADHYA., R.V.C.E.