embedded system lect6

8/18/2019 Embedded System Lect6

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Embedded System

Spring, 2011

Lecture 6: Branch, Call and Time Delay Loop

Eng. Wazen M. Shair


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2IUG- Embedded System

Today’s Lecture

Branch in!truction! and looping


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Branch in!truction! and looping

Looping in "#C

Loop in!ide loop

$ther conditional %ump!

&ll conditional ranche! are !hort %ump! Calculating the !hort ranch addre!!

'nconditional ranch in!truction


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Looping in "#C

(epeat a !e)uence o* in!truction! or a certain

numer o* time!

T+o +ay! to do looping

'!ing DECS- in!truction '!ing B-/B- in!truction!


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DECS- in!truction

Decrement *ile regi!ter, !0ip the ne1t in!truction i*

the re!ult i! e)ual 2

DECS- *ile(e*, d

3$T$ in!truction *ollo+! DECS-


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E1ample

Write a program to

a4 Clear W(E3

4 &dd 5 to W(E3 ten time! and place the

re!ult in S( "$(TB


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Solution

C$'T EQU 217

MOVL d8928

MOV! C$'T

MOVL 2 &3 "##L 5

#E$!S% C$'T,

&OTO &3MOV! "$(TB


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Solution


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'!ing B-/B- in!truction!

Supported y "#C9 *amilie!

Early *amilie! !uch a! "#C96 and "#C9 doe!n;t

!upport the!e in!truction

The!e in!truction! chec0 the !tatu! *lag

Bac0


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E1ample

Write a program to

a4 Clear W(E3

4 &dd 5 to W(E3 ten time! and placethe re!ult in S( "$(TB


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Solution

C$'T EQU 217

MOVL d8928MOV! C$'T

MOVL 2 &3 "##L 5

#E$! C$'T,

'(% &3MOV! "$(TB


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Solution


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E1ample

What i! the ma1imum numer o* time! that

the loop can e repeated=

&ll location! in the ile(eg are >it

The ma1. loop !ize i! 77 time


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Loop in!ide a loop

Write a program to

a4 Load the "$(TB S( regi!ter +ith the ?alue 77@

4 Complement "$(TB )00 time!

Solution(9 EQU 217

( EQU 216

C$'TA9 EQU d8928

C$'TA EQU d828

*+1


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Solution

MOVL 2177

MOV! "$(TB

MOVL C$'TA9

MOV! (9

L$"A9 MOVL C$'TA

MOV! (

L$"A $OM-! "$(TB,

DECF R2, F

BNZ LOP_2

DECF R1, F

BNZ LOP_1

Address Data

25H

(R1) 10

26H

(R2) 70

…

…

F81H(PO

RTB) 55


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Looping 922,22o time!

Becau!e t+o regi!ter! gi?e u! a ma1imum

?alue o* 6727, +e can u!e three regi!ter!

to get up to more 96 million iteration!


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$ther conditional %ump!


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B- Branch i* -94

The - *lag i! chec0ed #* it high it %ump! to the target addre!!.

or e1ample

$E( "$(TB, W F- $E(

#n thi! e1ample , i* "$(TB i! zero, it %umpe to the

lael $E(


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E1ample 5>7

Write a program to determine i* the loc. 2152

contain! the ?alue 2. i* !o, put 77@ in it.

Solution:

M.LO$ EG' $152MOV! MHL$C,

'(% EIT

MOVL 2177

MOV! MHL$CEIT ...


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BC ranch i* no carry4

The carry *lag it in the !tatu! regi!ter i! u!ed toma0e the deci!ion +hether to %ump.

#* it c24, the C"' !tart! to *etch and e1ecute

in!truction! *rom the addre!! o* the lael.

#* it c94, the C"' +ill e1ecute the in!truction elo+BC


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E1ample

ind the !um o* the ?alue! J@, 7@, andE@. "ut the !um in *ile(eg loc. 7@ and

6@.


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Guiz


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26IUG- Embedded System 26

(e*erence!

Fie @u , ECE6J Emedded ComputingSy!tem! , all 292.

PIC Microcontroller And Embedded Systems:

using Assembly and C for PIC 18 , M. Mazidi, (.

McKinlay and D. Cau!ey, "rentice all, 22.

Eng. @u!am &lza), Embedded System Course,

IUG, !1!

embedded system lect6

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