Page 406 - FUNDAMENTALS OF COMPUTER

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406 Fundamentals of Computers NPP

DEC CX
JNZ d 8

 But no flags are affected by LOOP · {H$ÝVw LOOP BÝñQ´>ŠeZ go H$moB© ^r âcoJ à^m{dV
instruction. Zht hmoVm h¡&

LOOPE d 8 Loop while equal
or LOOZ d 8 Loop while zero.

 It decrements CX by one and jumps to · `h CX _| 1 KQ>mVm h¡ VWm {ZYm©[aV {S>gßcog_oÝQ>
specified displacement d only when d _| Oån H$aVm h¡ O~ (CX) ≠ 0 VWm ZF = 1.
8
(CX) ≠ 0 and ZF = 1. 8
 It may be used just after compare instruc- · Bgo H$åno`a BÝñQ´>ŠeZ Ho$ R>rH$ ~mX _| Cn`moJ {H$`m
tion. Program control will jump to speci- Om gH$Vm h¡& àmoJ«m_ H$ÝQ´>moc {ZYm©[aV {S>gßcog_oÝQ>
fied displacement only when (CX) ≠ 0 and
both the operands are equal. na Oån H$aoJm O~ (CX) ≠ 0 VWm XmoZm| Am°naoÝS²>g
~am~a h¢&
LOOPNE d 8
or LOOPNZ d 8
Loop while not equal or Loop while no byn O~ g_mZ Z hmo `m byn O~ Zmo Oramo hmo& d na
8
zero. Jump at d only when, (CX) ≠ 0 and ZF = Oån H$aoJm O~ (CX) ≠ 0 VWm ZF = 0 {H$ÝVw nhco CX _|
8
0. But first decrement CX by 1.
1 KQ>mVm h¡&
JCXZ d : Jump if (CX) = 0
8
This instruction is used just before starting `h BÝñQ´>ŠeZ narjU H$aZo Ho$ {cE cyn Ho$ àmaå^
the Loop to test whether the count in CX is hmoZo Ho$ R>rH$ nhco Cn`moJ {H$`m OmVm h¡ {H$ Š`m CX _|
zero.
g§»`m eyÝ` h¡&
Interrupt Instruction (Software Interrupts) BÝQ>aßQ> BÝñQ´>ŠeZ (gm°âQ>do`a BÝQ>aßQ²>g)
Software Interrupts are similar to CALL gm°âQ>do`a BÝQ>aßQ²>g CALL BÝñQ´>ŠeZ Ho$ g_mZ
instructions except that the contents of flag hmooVo h¢, AÝVa `h h¡ {H$ âcoJ a{OñQ>a Ho$ H$ÝQ>oÝQ²>g ^r
Register also pushed on to stack.
ñQ>¡H$ na ^oOo OmVo h¢&
INT n
where, n = 0 to 255
: Interrupt type n;
Flags, CS and IP contents are pushed on âco½g, CS VWm IP ñQ>¡H$ na ^oOo OmVo h¢& CS VWm
stack. CS and IP both are loaded from four IP XmoZm| {\${OH$c ES´>og 4n na àmaå^ hmoZo dmco Mma
locations starting at physical address 4n.
cmoHo$eÝg go cmoS> {H$`o OmVo h¢&
Following sequence of operations take Am°naoeÝg H$m {ZåZ{c{IV {gŠdoÝg hmoVm h¡:
place:
1. Flag Register is pushed on the stack. 1. âcoJ a{OñQ>a H$mo ñQ>¡H$ na ^oOm OmVm h¡&
2. IF ← 0, TF ← 0 (Both IF and TF are cleared) 2. IF ← 0, TF ← 0 (IF VWm TF XmoZm| Šcr`a hmo OmVo h¢)