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Logic Instructions

The logic instructions include

AND

OR

XOR (Exclusive-OR)

NOT

TEST

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Alloed o!er"nds #or AND$ OR$ "nd

XOR instructions

Alloed o!er"nds #or NOT instruction

Logic instructions % AND$ OR$ XOR$ NOT

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EXA&'LE

Descrie the results o# executing the #olloing instructions

&O* AL$ +,+,+,+,

AND AL$ +++,,,,,

OR AL$ ,,++++++

XOR AL$ ++++,,,,

NOT ALSolution%

Executing the AND instruction$ e get

(AL).+,+,+,+,/ +++,,,,,/. +++,+,+,/.,0,1Executing the OR instruction$ e get

(AL). +++,+,+,/2 ,,++++++/. ,,+,+,+,/.D0,1

Executing the XOR instruction$ e get

(AL). ,,+,+,+,/ ++++,,,,/. ,,+,,+,+/.DA,1Executing the NOT instruction$ e get

(AL). (NOT),,+,,+,+/. ++,++,+,/./0,1

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EXA&'LE

Masking and setting bits in a register.

&"s3 o# the u!!er ,/ its o# the ord o# d"t" in AX

AND AX$ +++4,1

&O* AL$ 56ONTROL74LA8S9

OR AL$ ,+:

&O* 56ONTROL74LA8S9$ AL

(AL).XXXXXXXX/2+++,++++/. XXX,XXXX/

Setting ; o# the

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TEST inst!"tion #$%oms th$ &N' o#$ation

TEST do$sn(t "han)$ th$ d$stination o#$and. E%%$"ts onl* th$ %la) $)ist$

Sam$ add$ssin) mod$ as &N'

TEST %!n"tions sam$ as +- !t t$st onl* a

sin)l$ it.

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Shi#t instructions% S:L$ S:R$ SAL$ SAR

Alloed o!er"nds #or shi#t instructions

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0010110001001000

0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 00

it 0

0&

&%t$

&

$%o$

+

Result of executing SHL AX,1

it 0it 15

it 15

Result of executing SHR AX,1

0010110001001000

0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0

it 0

0

&

$%o$

0

+

it 0

it 15

it 15

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EXA&'LE

Assu=e th"t 6L cont"ins +/,1 "nd AX cont"ins +>,A,1?

Deter=ine the ne contents o# AX "nd the c"rr< #l"g "#ter

the instruction SAR AX$ 6L is executed?

Solution%

(AX).++++++,++,+++,,+/.+/;1,1

"nd the c"rr< #l"g is (64).,/

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SAR AX,CL

0101100010010000

0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0

it 0

&

$%o$

1

+

it 0

it 15

it 15

&

&%t$

MOV CL,02H

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EXA&'LE

Isol"te the it @ o# the

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0010110001001000

0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0Bit 0

0

AX

After

AX

Before

CF

Result of executing ROL AX,1

Bit 0Bit 1

Bit 1

0

CF

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AX

After

AX

Before

Result of executing ROR AX,CL !it" #CL$%&

0010110001001000

Bit 0

0

CF

Bit 0Bit 1

Bit 1

0

CF

0 1 0 0 0 0 0 1 0 0 1 0 0 0 1 1

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Bit 1 Bit 0CF

Rotation "a!s$d * $6$"!tion o% th$ R+7 inst!"tion

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EXA&'LE

Bh"t is the result in X "nd 64 "#ter execution o# the #olloing

instructions

R6R X$ 6L

Assu=e th"t$ !rior to execution o# the instruction$ (6L).+;,1$

(X).,/@;,1$ "nd (64).+Solution%

The origin"l contents o# X "re

(X) . +++,++,+++,,+,++/ . ,/@;,1

Execution o# the R6R co=="nd c"uses " ;-it rot"te right

through c"rr< to t"3e !l"ce on the d"t" in X$ the results "re

(X) . ,++++++,++,+++,,/. C,/@,1 (64) . +/