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 Post subject: Help with basic code
PostPosted: Wed Jan 15, 2020 12:34 pm 

Joined: Fri Dec 13, 2019 8:57 am
Posts: 2
Hello everyone!

I am trying a new programme, easier than the other but I'm a little stuck with the code, I was studying a bit more (searching text in spanish) and now I think I understand this type programming mode a little,

So my first program is about simply arithmetics, I have two constants 70 and 150 and I have to make the sum and then divide the result by 2, so here is my first try:

Exercise   IDNT   1,1           *Program name
      ORG   $2000   *Location of the program
      JMP   Inicio   *Jump to first instruction

A      DC.W   70   *Give A the value 70
B      DC.W   150   *Give B the value 150
Suma   DS.W   1   *Result of the sum
Enc      DS.W   1   *Total result

Main program
Inicio   MOVE.W A,D0   *Copy variable to register D0
      MOVE.W B,D1   *Copy variable to register D1
      ADD.W D0,D1   *Sum the values of D0 and D1
      MOVE.W D1,Suma   *Storage the result in Suma
      MOVE.w Suma,D2   *Copy variable to register D2
      DIVU D2/#2               *Make Suma/2
      MOVE.W Enc,D2   *Copy variable to register D2
Fin      STOP #$2700   *Ends program

I think the result is storaged in D2...right?

Ok and secondly I have to write a program which have to write a message if the number is lower than 500, if is between 500 and 1000 and if is greater than 1000

Ejercicio IDNT 1,2
ORG $2000
JMP Inicio
Val1 EQU 232 *This is the def o the value cause I don't know how to read an imput value

Ingreso DC.W Val1
Min DC.W 500 *Give Min the value 500
Max DC.W 1000 *Give Max the value 1000
Msg1 DC.B 'Los ingresos han sido < 500'
Msg2 DC.B 'Los ingresos han sido > 500 e < 1000'
Msg3 DC.B 'Los ingresos han sido > 1000'

Main program
Start MOVE.W Min,D0 *Copy variable Min to register D0
MOVE.W Max,D1 *Copy variable Max to register D0
MOVE.W Val1,D2 *Copy variable Val to register D2
If1: *first conditional
CMP.W D2,D0 *Compare registers D0-D2
BHI.S else1 *Jump if D2 < D0
LEA Msg1,A1 *Loads message 1 in register A1
MOVE.B #14,D0 *Copy number 14 to adress D0 for task 14
TRAP #15
BRA.S finif1
finif1: *end of first conditional
If2: *second conditional
BHI.S else1 *Jump if D2 > D0
LEA Msg2,A2
MOVE.B #14,D0
TRAP #15
BRA.S finif1

BHI.S else1
LEA Msg2,A2
MOVE.B #14,D0
TRAP #15
BRA.S finif1


I have problems with the third condition because I don't know how to add the >500 AND <1000

Someone please can explain me the conditionals? something similar to write this on assambler;

IF <condition>

Also the use of AND please

IF <condition AND condition>

 Post subject: Re: Help with basic code
PostPosted: Thu Feb 20, 2020 9:06 pm 

Joined: Thu Feb 20, 2020 8:02 pm
Posts: 11
Hello !

1 If you have 2 positive constants 70 and 150 want to add them then divide by two, the simplest is
        constant1: dc.b 70
        constant2: dc.b 150
        move.w constant1,d0
        add.w constant2,d0 ; you can add from memory, no need to load into a register first
        lsr.w #1,d0  ; for dividing/multiplying by powers of 2, bit shifting is much quicker that divu!

2 About how to represent an "AND" condition: you test each condition in sequence and after each test, you branch out if the condition is false. e.g.
if:      tst.w <condition1>
         bne  else
         tst.w <condition2>
         bne else
then: ...do something
         bra endif
else:  ... do something else

For you, the tests will be
        cmp.w #1000,d0
        bhs else
        cmp.w #500,d0
        bls else

testing if d0 >= 1000 (cmp.w #1000,d0and d0 >= #501 and use bhs
Does it make sense ?

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