stuffy 6502

examples/count.asm

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+; count.asm - prints "0123456789" then a newline and halts.
+; Exercises ADC, CMP, branches and a loop.
+
+        .export start
+
+start:
+        lda #'0'
+loop:
+        sta $F001
+        clc
+        adc #$01
+        cmp #$3A          ; '9' + 1
+        bne loop
+        lda #$0A          ; newline
+        sta $F001
+        lda #$00
+        sta $F003
+        rts

examples/hello.asm

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+; hello.asm - single-object demo.
+; Prints "Hello, World!" through the memory-mapped terminal at $F001,
+; then writes to the halt register at $F003.
+
+        .export start
+        .org $0600
+
+        jmp start
+
+msg:
+        .asciiz "Hello, World!"
+
+start:
+        ldx #0
+loop:
+        lda msg,x
+        beq done
+        sta $F001
+        inx
+        jmp loop
+done:
+        lda #$00
+        sta $F003
+        rts

examples/main.asm

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+; main.asm - cross-object demo, part 2.
+; Imports `putc` from putc.wo and prints "Hello, 6502!".
+
+        .export start
+        .import putc
+
+        jmp start
+
+msg:
+        .asciiz "Hello, 6502!"
+
+start:
+        ldx #0
+loop:
+        lda msg,x
+        beq done
+        jsr putc
+        inx
+        jmp loop
+done:
+        lda #$00
+        sta $F003
+        rts

examples/putc.asm

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+; putc.asm - cross-object demo, part 1.
+; Exports `putc`: write the byte in A to the terminal and return.
+; This object is relocatable; the linker places it at the load address.
+
+        .export putc
+
+putc:
+        sta $F001
+        rts