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Thanh Van
Thanh Van

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SPO600 - Lab 4 - Option 1

In the previous lab, we were working with Math in Assembly Language. However, in this lab, we will be working on Assembly Language String. We have four options to pick this time, and implement two of them:

  • Adding Calculator
  • Data Input Form
  • Hexdump
  • Screen Colour Selector

For the first option, I choose Adding Calculator to work on.

Instruction

  1. Create a subroutine which enables the user to enter two numbers of up to two digits. Indicate where the cursor is, and allow the user to use the digit keys (0-9), backspace, and enter keys. Return the user's input value in the accumulator register.
  2. Using this subroutine, write a program which add the two numbers (each of which is in the range 0-99) and print the result.

Program

; ======== variables for screen input/output ========
define  SCINIT  $ff81 ; initialize/clear screen
define  CHRIN  $ffcf ; input character from keyboard
define  CHROUT  $ffd2 ; output character to screen
define  SCREEN  $ffed ; get screen size
define  PLOT    $fff0 ; get/set cursor coordinates

; ======== variables for key ========
define RIGHT  $81
define LEFT  $83
define ENTER  $0d
define BACKSPACE $08

; numbers given by user
define NUM1    $15;
define  NUM2    $16;

        jsr SCINIT

; prompts to get input from user, do calculation and print the result
mainLoop:
     ldy #$00
     jsr firstNumPrint ; ask for input for first number
     jsr getNum; get the first number
     jsr storeFirstNum  ; then store the first number
     ldy #$00
     jsr secondNumPrint  ; ask for input for second number
     jsr getNum; get the second number
     jsr storeSecondNum  ; store the second number
     ldy #$00
     jsr resultPrintString  ; print a string 'Result'
     jsr printResult ; print the result
     jmp mainLoop  ; go back to the first step


getNum:
     sec
     jsr PLOT
     ldx #$15
     clc
     jsr PLOT

getNumLoop:
     sec
     jsr PLOT
     jsr CHRIN


charCheck: 
     cmp #BACKSPACE ; if user enter backspace, it erase the #$15 digit
 beq move_back

     cmp #RIGHT ; if user enter right arrow, it goes to the first digit
     beq move_right

     cmp #LEFT ; if user enter left arrow, it goes to the second digit
     beq move_left

     cmp #ENTER ; if user enter enter, it goes to the next process
     beq move

drawNum:
; check whether user enters number (#$30-#$39)
     cmp #$30
     bcc getNumLoop

     clc
     cmp #$3a
     bcs getNumLoop

     jsr CHROUT

     sec
     jsr PLOT
     cpx #$17
     bne getNumLoop
     dex
     clc
     jsr PLOT
     jmp getNumLoop

move_back:
 cpx #$15
 beq getNumLoop
 jsr CHROUT
 jmp getNumLoop

move_left: 
 cpx #$15 ; first digit
     beq getNumLoop
     jsr CHROUT
     jmp getNumLoop

move_right: 
 cpx #$16 ; second digit
     beq getNumLoop
     jsr CHROUT
     jmp getNumLoop

move:
     sec
     jsr PLOT
     ldx #$15 ; first degit
     clc
     jsr PLOT
     sec
     jsr PLOT

     clc
     sbc #$2F ; to calculate it, it should be subtracted by #$2f

     asl
     asl
    asl
     asl

     pha

     ldx #$16
     clc
     jsr PLOT
     sec
     jsr PLOT

     clc
     sbc #$2F ; to calculate it, it should be subtracted by #$2f
     pha

     ldx #$00
     iny
     clc
     jsr PLOT
     sec
     jsr PLOT

     pla
     tax
     pla

     rts

; store the first number
storeFirstNum:
     sta NUM1
     txa
     eor NUM1
     sta NUM1
     rts

; store the second number
storeSecondNum:
     sta NUM2
     txa
     eor NUM2
     sta NUM2
     rts

; print out the result
printResult:
     sec
     jsr PLOT
     ldx #$15
     clc
     jsr PLOT
     sec
     jsr PLOT

     sed
     lda NUM1
     adc NUM2
     cld
     pha

     bcc outputAddition
     ldx #$14
     clc
     jsr PLOT
     sec
     jsr PLOT
     lda #$31
     jsr CHROUT

; calculation of the two number
outputAddition:
     lsr
     lsr
     lsr
     lsr
     clc
     adc #$30 ; as the received number does not fit for ASCII, it needs to add #$30
     jsr CHROUT

     pla
     and #$0F
     clc
     adc #$30 ; as the received number does not fit for ASCII, it needs to add #$30
     jsr CHROUT

     sec
     jsr PLOT
     ldx #$00
     iny
     clc
     jsr PLOT

     rts

; prompt to get first number, format "00"
firstNumPrint:
 lda firstNum,y
        beq goback_main
        jsr CHROUT
        iny
        bne firstNumPrint

; prompt to get the second number, format "00"
secondNumPrint:
 lda secondNum,y
        beq goback_main
        jsr CHROUT
        iny
        bne secondNumPrint

; print our the result line
resultPrintString:
 lda result,y
        beq goback_main
        jsr CHROUT
        iny
        bne resultPrintString

; go back to the "mainLoop"
goback_main:
     rts


firstNum:
dcb "E","N","T","E","R",32,"F","I","R","S","T",32,"N","U","M","B","E","R",":",32,32,"0","0"
dcb 00


secondNum:
dcb "E","N","T","E","R",32,"S","E","C","O","N","D",32,"N","U","M","B","E","R",":",32,"0","0"
dcb 00

result:
dcb "R","E","S","U","L","T",":"
dcb 00

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What I have learned from this lab?

This lab definitely takes a lot of my time, I always encounter error related to subroutines. Since I am not used to Assembly Language yet, however, this is why I have to spend some times working on it.

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