CHAPTER 6

PROGRAM CONTRAL INSTRUCTIONS

PROGRAM CONTRAL INSTRUCTIONS

direct the flow of a program and allow the flow to Change.

JUMP (BMP)

The main program control instruction, allows the programmer to skip sections of a program and branch to any part of the memory for the next instruction.

CONDITIONAL JUMP

allows the programmer to make decisions based upon numerical tests.

FLAG BITS

The results. of numerical tests are held

short jump

near jump

- Far jump

THREE TYPES OF UNCONDITIONAL JUMP INSTRUCTIONS

SHORT JUMP

- is a 2 byte instruction that allows jumps or branches to memory location within +127 and -128 Following bytes from the address the jump.

NEAR JUMP

The 3 byte allows a branch or jump within ± 32k bytes from the instruction in the current code segment.

fAR JUMP

The s byte allows a jump to any memory location within the real memory system

INTRASEGMENT JUMPS

short and near jumps are often called

INTERSEGMENT JUMPS

Far jumps are often called

SHORT JUMP (2)

are called relative jumps

SHORT JUMP (2)

because they can be moved, along with their relative software, to any location in in the current code segment without change.

SHORT JUMP DISPLACEMENT

- is a distance represented by a 1-byte signed numbers whose value ranges between +127 and -128

LABEL

a symbolic name for a memory address

NEAR JUMP

similar to the short jump, except that the distance is Farther

NEAR JUMP

it passes control to an instruction in the current code segment located within 132K bytes jump instructions,

EXTERNAL LABELS

appears in programs that contain more then one program file

INDIRECT JUMP

it can also use as as, 16 or 32 bit register as an operaand This will automatically as

CONDITIONAL JUMP

are always short jump in the 8086 through the microprocessor.

sign

-carry

-overflow

-parrity

CONDITIONAL FLAG BITS

Jg

JGE

-JE

- JL

-JLE

- JNE

SIONED NUMBERS ARE COMPARED

( greater than less than)

JA

- JAB

- JE

JB

- JBE

-JNE

UNSIGNEDC ABOVE & BELOW)

CONDITIONAL GET INSTRUCTIONS

Addition to the conditional jump instructions.

LOOP

is a combination OF a decrement ex and JNZ conditional jump.

WHILE

used with a condition to begin the loop

ENDW

ends the loop

REPEAT UNTIL CONSTRUCT

A series of instructions is repeated until some condition occurs.

REPEAT

defines the start Of the loop

UNTIL CX2 instruction

available that uses the Loop instructions

to check CX For a repeat loop.

UNTIL CX2 instruction

used to add the contents of byte-sized array ONE to byte size ARRAY TWO

PROCEDURE (subroutine, method, or function

is an important part of any computer system's architecture

PROCEDURE (subroutine, method, or function

is a group of instructions that usually performs one task

PROCEDURE (subroutine, method, or function

-is a reusable section of the software that is stored in memory once,

CALL Instructions

-it pushes the address of the instruction following the return address on the stack

PROC DIRECTIVES

The procedure begin with this

END DIRECTIVES

END DIRECTIVES

NEAR Or FAR

The PROC directive is followed by the type of procedure.

USES STATEMENT

allows any number of registers to be automatically pushed to the stack and popped from the stack within the procedure

NEAR RETURN

removes a 16 bit number from the stack and places into the instruction pointer to return from the procedure in the curent code segment.

fAR RETURN

removes a 32 bit number from the stack and places it into both Ip and CS to return from the procedure to any memory location

HARDWARE-GENERATED CALL

externally derived from a hardware signal

SOFTWARE -GENERATED CALL

internally derived From the execution OF on instruction or by some other internal event.

EXCEPtion

an internal interrupt is called

INTERUPT VECTOR

is a 4 byte number stored in the first 1024 bytes of the memory when the microprocessor operates in the real mode

INT, INTO, INT3

The microprocessor has 3 different interrupt instructions that are available to the program.

INTS (Interrupt instructions

INTS (Interrupt instructions

IRET/IRETD Interrupt return instructions)

is used only with software or hard ware interrupt service procedure

INT 3

is a interrupt special software interuppt designed to Function as a breakpoint.

BREAKPOINT

occurs For any software interuppt.

helps to debug Faulty soptare

INTO (Interrupt on overflow)

is a conditional soptware interrupt that tests the overflow.

INTO (Interrupt on overflow)

appears in software that adds or subtract Signed binary number.

sET INTERRUPT FLAG CLEAR INTERRUPT

These instructions. control the INTR pin

SET INTERRUPT FLAG (STI

places a 1 into the Flag I Flag bit, which enables the INTR pin.

•CLEAR INTERRUPT FLAG (CLI)

places a O into the Iflag bit, which disables the INTR pin

MACHINE CONTROL and MISCELLANEOUS

These instructions provide control of the carry bit.

STC (set carry), cic (clear (arry), CMC (complement carry)

3 instructions control the contents of the carry Flag.

by an interrupt

- by a hardware reset

during a DMA operation

3 WAYS TO EXIT A HALT

NOPC No operation)

often used to pad soptware with space For future machine language

BOUND

is a comparison instruction that may cause an interrupt.