Page 402 - FUNDAMENTALS OF COMPUTER

402 Fundamentals of Computers NPP

[ S I]
[SI + 1] IP
[SI + 2]
[SI + 3] CS

 But remember the sequence of PUSH. First · {H$ÝVw PUSH H$s {gŠd|g `mX aI|& nhco CS H$mo
CS is pushed and loaded then IP is pushed ^oOm OmVm h¡ VWm BgHo$ níMmV² IP H$mo ^oOm VWm
and loaded. cmoS> {H$`m OmVm h¡&
RET
Return to Calling Program: This instruc- H$m°qcJ àmoJ«m_ ‘| dmngr: `h BÝñQ´>ŠeZ EH$ g~éQ>rZ
tion is used to return to the main program go _w»` àmoJ«m_ _| dmng AmZo Ho$ {cE Cn`moJ {H$`m OmVm h¡
from a subroutine which was called by CALL
Instruction. Therefore it is used at the end of {Ogo CALL B§ñQ´>³eZ H$m°c {H$`m J`m Wm& Bg{cE `h
subroutine. g~éQ>rZ Ho$ AÝV _| Cn`moJ {H$`m OmVm h¡&
 For Intrasegment CALL following opera- · BÝQ´>mgoJ_oÝQ> CALL _| {ZåZ{c{IV Am°naoeÝg
tions take place: NPP hmoVo h¢:

"IP is loaded from top of the stack" IP ñQ>¡H$ Ho$ Q>m°n go cmoS> {H$`m OmVm h¡&
It is equivalent to POP IP. `h POP IP Ho$ g_H$j h¡&
 For Intersegment CALL following opera- · BÝQ>agoJ_oÝQ> CALL _| {ZåZ{c{IV Am°naoeÝg
tions take place: hmoVo h¢:
1. IP is loaded from top of stack. 1. IP ñQ>¡H$ Ho$ Q>m°n go cmoS> {H$`m OmVm h¡&

(POP IP) (POP IP)
2. CS is loaded from top of stack 2. CS ñQ>¡H$ Ho$ Q>m°n go cmoS> {H$`m OmVm h¡&
(POP CS) (POP CS)
JMP d / JMP d : Jump; Unconditional JMP d / JMP d … Oån; {ZYm©[aV 8 {~Q> `m 16
8
16
8
16
jump to specified 8-bit or 16-bit signed dis- {~Q> gmBÝS> {S>gßcog_oÝQ> Ho$ {cE AZH$ÊS>reZc Oån h¡&
placement. The specified displacement is added {ZYm©[aV {S>gßcog_oÝQ> IP Ho$ H$ÝQ>oÝQ²>g _| Omo‹S>m OmVm h¡&
to contents of IP. Thus,
Bg àH$ma:
IP ⇐ IP ± displacement
 In both the cases CS remains unchanged · XmoZm| pñW{V`m| _| CS An[ad{V©V ahVm h¡, Bg[cE
therefore it is an example of Intrasegment `h BÝQ>agoJ_oÝQ> ~«mÝM BÝñQ´>ŠeZ H$m CXmhaU h¡&
branch instruction.

 Label can be specified in place of displace- · {S>gßcog_oÝQ> Ho$ ñWmZ na co~c {ZYm©[aV {H$`m Om
ment e.g. gH$Vm h¡&

JMP NEXT
JMP START