Added test ref

src/test/ref/mul8u-min.asm

@@ -0,0 +1,70 @@
+// Minimal test of mul8u
+.pc = $801 "Basic"
+:BasicUpstart(main)
+.pc = $80d "Program"
+main: {
+    .label screen = $400
+    .label _0 = 4
+    .label i = 3
+    .label a = 2
+    lda #0
+    sta i
+    sta a
+  b1:
+    ldy #0
+  b2:
+    ldx a
+    tya
+    jsr mul8u
+    lda i
+    asl
+    tax
+    lda _0
+    sta screen,x
+    lda _0+1
+    sta screen+1,x
+    inc i
+    iny
+    cpy #6
+    bne b2
+    inc a
+    lda #6
+    cmp a
+    bne b1
+    rts
+}
+// Perform binary multiplication of two unsigned 8-bit bytes into a 16-bit unsigned word
+// mul8u(byte register(X) a, byte register(A) b)
+mul8u: {
+    .label mb = 6
+    .label res = 4
+    .label return = 4
+    sta mb
+    lda #0
+    sta mb+1
+    sta res
+    sta res+1
+  b1:
+    cpx #0
+    bne b2
+    rts
+  b2:
+    txa
+    and #1
+    cmp #0
+    beq b3
+    lda res
+    clc
+    adc mb
+    sta res
+    lda res+1
+    adc mb+1
+    sta res+1
+  b3:
+    txa
+    lsr
+    tax
+    asl mb
+    rol mb+1
+    jmp b1
+}