Simple integer to hex print in 6502 assembly language

debug.asm

// This is for the Commodore 64 and requires KickAssembler
// Written by Cecil Meeks (cbmeeks) in 2023

// NOTE, this prints whatever is in A to the screen.  So load A first.

// First, create a simple macro:
.macro DebugText_A_Hex(X, Y) {
        sta ModA + 1                    // save A below
        stx ModX + 1                    // save X below
        sty ModY + 1                    // save Y below

        pha                             // push A to stack
        and #%00001111                  // grab lower nybble
        tay                             // move A to Y
        lda DEBUG.HEX, y                // lookup character from table
        sta $0400 + (Y * 40) + X + 1    // plot to screen at coordinates + 1

        pla                             // pull A off stack
        and #%11110000                  // grab upper nybble
        lsr
        lsr
        lsr
        lsr                             // move to lower nybble
        tay                             // move A to Y
        lda DEBUG.HEX, y                // lookup character from table
        sta $0400 + (Y * 40) + X        // plot to screen at coordinates

        // restore everything 
        ModA: lda #$00
        ModX: ldx #$00
        ModY: ldy #$00
}


// table used (resides in a class)


DEBUG: {

    HEX:    {
        .byte $30, $31, $32, $33, $34, $35, $36, $37, $38, $39  // 0-9
        .byte $01, $02, $03, $04, $05, $06                      // A-F
    }

}