refactor(memtest): refactored the port of ROBIT-2

code/boot/src/boot.s

@@ -73,29 +73,27 @@ OUTSTR
 ; RAM testing routine. Ported to 6809 from 6800, based on source for ROBIT-2 for
 ; MIKBUG.
 RAMTEST
-  ldx #SRAM_BASE       ; Store 1 in memory
-  lda #1
+  ldx #SRAM_BASE
+1                      ; Store 1 in memory
+  lda #1               ; Set [X] to 1
   sta 0,x
-  cmpa 0,x
-  bne 1F
-1                      ; Loop point for next
+  cmpa 0,x             ; If failed print out an error indicator
+  bne 3F
+2                      ; Loop point for next address
   asla                 ; Shift A and [X] left
   asl 0,x
-  cmpa 0,x
-  bne 1F
+  cmpa 0,x             ; Compare A and [X]
+  bne 3F
   cmpa #$80            ; Only test up to $80
-  bne 1B
-  bra 2F
-1                      ; Write out error indicator
+  bne 2B               ; Loop if not $80
+  cmpx #$60FF          ; Compare X to end of RAM
+  beq 4F               ; Finish if we're at the end
+  leax 1,x             ; Increment X
+  bra 1B
+3                      ; Write out error indicator
   ldb #'X
   jsr OUTCHAR
-  bra 3F               ; Branch to finish
-2
-  cmpx #$60FF          ; Compare X to end of RAM
-  beq 3F               ; Finish if done, else try next address
-  leax 1,x
-  bra RAMTEST
-3
+4                      ; Pass test
   ldb #'P
   jsr OUTCHAR
   rts