Easiest program in 6502 emulator part-2

; input5 :: get 5 uppercase letters from the user
;
; An example of a text input routine.
;
; Chris Tyler 2023-01-12
; (C)2023 Seneca College of Applied Arts and Technology
; Licensed under the terms of the GPL v2+ – See the
; LICENSE or COPYING file for details.
;
; Works with the 6502 emulator at http://6502.cdot.systems
;

; ROM routines
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
define ZERO_ASCII $30

; Memory locations
define INPUT $2000 ; input buffer (up to 5 chars)

;
; This routine get a 5-character word from the user. Only letters
; can be accumulated. The backspace key deletes the last character
; if the character count is >0. The ENTER key accepts the input
; if the character count is 5. Lower case letters are converted to
; UPPERCASE.

JSR SCINIT

LDY #$00
PROMPT_CHAR:
LDA PROMPT_TEXT,Y
BEQ DONE_PROMPT
JSR CHROUT
INY
BNE PROMPT_CHAR

DONE_PROMPT:
JSR GET_INPUT

LDA #$0D
JSR CHROUT

LDY #$00
INPUT_PRINT:
LDA INPUT,Y
JSR CHROUT
INY
CPY #$05
BNE INPUT_PRINT
JMP Colouring

PROMPT_TEXT:
dcb “I”,”f”,32,”y”,”o”,”u”,32,”w”,”a”,”n”,”t”,32,”t”,”o”,32,”s”,”e”,”e”,32
dcb “m”,”a”,”g”,”i”,”c”,32,”t”,”h”,”e”,”n”,32,”t”,”y”,”p”,”e”,32,”m”,”a”,”g”,”i”,”c”,32,”a”,”n”,”d”,32,”p”,”r”,”e”,”s”,”s”,32,”e”,”n”,”t”,”e”,”r”,32,”t”,”w”,”i”,”c”,”e”,32,00

; —————————————————————

GET_INPUT:
LDA #$A0 ; CODE FOR BLACK SPACE
JSR CHROUT
LDA #$83 ; CODE TO MOVE CURSOR LEFT ONE POSITION
JSR CHROUT

LDY #$00 ; COUNT OF CHARACTERS TYPED

GET_CHAR:
JSR CHRIN
CMP #$00
BEQ GET_CHAR

CMP #$08 ; COMPARE INPUT CHAR WITH BACKSPACE
BNE CHECK_ENTER ; … IF NOT BS, THEN CHECK FOR ENTER

CPY #$00 ; COMPARE CHAR COUNT WITH 0
BEQ GET_CHAR ; … IF EQUAL THEN GET ANOTHER CHAR

DEY
LDA #$20 ; LOAD A WITH CODE FOR WHITE SPACE
JSR CHROUT
LDA #$83 ; CODE TO MOVE CURSOR LEFT ONE POSITION
JSR CHROUT
JSR CHROUT
LDA #$A0 ; CODE FOR BLACK SPACE
JSR CHROUT
LDA #$83 ; CODE TO MOVE CURSOR LEFT ONE POSITION
JSR CHROUT

CHECK_ENTER:
CMP #$0D ; COMPARE INPUT CHAR WITH ENTER
BNE CHECK_LETTER ; … IF NOT ENTER, CHECK FOR LETTERS
CPY #$05 ; SEE IF WE HAVE 5 CHARACTERS
BEQ DONE_INPUT ; IF WE HAVE 5 CHARS, AND THE USER PRESSED ENTER, DONE!

CHECK_LETTER:
CMP #97 ; COMPARE INPUT CHAR WITH ‘a’
BCC UPPERCASE ; … IF LOWER, CHECK IF IT’S UPPERCASE

CMP #123 ; COMPARE INPUT CHAR WITH ‘z’ + 1
BCS GET_CHAR ; … IF HIGHER THAN ‘z’ THEN GET ANOTHER CHAR

SEC
SBC #32 ; SUBTRACT 32 TO CONVERT lowercase TO UPPERCASE

UPPERCASE:
CMP #65 ; COMPARE INPUT CHAR WITH A C=1 IF A>=65 ; C=0 IF A<65
BCC GET_CHAR ; … IF LOWER THAN ‘A’ THEN GET ANOTHER CHAR

CMP #91 ; COMPARE INPUT CHAR WITH Z + 1
BCS GET_CHAR ; … IF HIGHER THAN ‘Z’ THEN GET ANOTHER CHAR

CPY #$05 ; CHECK THE COUNT OF CHARACTERS
BEQ GET_CHAR ; … IF WE HAVE 5 WE CAN’T ACCEPT ANOTHER ONE

STA INPUT,Y
JSR CHROUT ; PRINT RECEIVED LETTER ON THE SCREEN

LDA #$A0 ; CODE FOR BLACK SPACE
JSR CHROUT
LDA #$83 ; CODE TO MOVE CURSOR LEFT ONE POSITION
JSR CHROUT

INY

JMP GET_CHAR

DONE_INPUT:
LDA #$20 ; LOAD A WITH CODE FOR WHITE SPACE
JSR CHROUT

Colouring:
lda #$07 ; colour number
ldy #$00 ; set index to 0
loop: sta $0200,y ; set pixel colour at page 2+y
sta $0300,y ; set pixel colour at page 3+y
sta $0400,y ; set pixel colour at page 4+y
sta $0500,y ; set pixel colour ar page 5+y
iny ; increment index
bne loop ; continue until done the page (256 pixels)
jmp PROMPT_CHAR2

LDY #$00
PROMPT_CHAR2:
LDA Statement,Y
BEQ Addition
JSR CHROUT
INY
BNE PROMPT_CHAR2

LDY #$00
PROMPT_CHAR3:
LDA FinalStatement,Y
BEQ End
JSR CHROUT
INY
BNE PROMPT_CHAR3

Statement:
dcb “1”,32,”+”,32,”2″,32,”=”
FinalStatement:
dcb 32,”F”,”i”,”n”,”d”,32,”o”,”u”,”t”,32,”h”,”o”,”w”,00

Addition:
LDA #01
CLC
ADC #02
JSR CHROUT
STA $0402
JSR PROMPT_CHAR3

End:
BRK