Page 320 - FUNDAMENTALS OF COMPUTER
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320 Fundamentals of Computers NPP
Difference and borrow we can draw the logic ~m°amo H$s ghm¶Vm go h‘ BgHo$ {bE bm°{OH$ g{H©$Q> ~Zm
circuit for this as: gH$Vo h¢…
3.49 Full Subtractor 3.49 \w$b g~Q´>oŠQ>a
Definition: n[a^mfm…
"It is a combination logic circuit which can ""`h EH$ Eogm H$m§{~ZoeZb Vm{H©$H$ n[anW h¡ Omo
perform arithmetic subtraction over three bits." VrZ {~Q>m| na KQ>mZo H$s {H«$`m H$aVm h¡ Ÿ&''
Block Diagram ãbm°H$ S>m`J«m_
It has three inputs; A, B and C but two Bg_| VrZ BZnwQ> A, B VWm C hmoVo h¢Ÿ& Xmo AmCQ>nwQ>
outputs; difference and Borrow: Difference d Borrow hmoVo h¢…
A Borrow
Full
B Subtractor
C Difference
= A-B-C
Truth Table gË`-Vm{cH$m
Difference
A B C Borrow
=A–B–C
0 0 0 0 0
0 0 1 1 1
0 1 0 1 1
0 1 1 1 0
1 0 0 0 1
1 0 1 0 0
1 1 0 0 0
1 1 1 1 1
From the truth table it is clear that gË` Vm{bH$m go ñnï> h¡ {H$ Difference Vmo EH$
difference can be obtained by one 3-input XOR 3-BZnwQ> XOR JoQ> go àmá {H$`m Om gH$Vm h¡ Ÿ& na§Vw
gate: The Borrow can be found using K-map Borrow hoVw K-map ~ZmZm hmoJm…
technique:
