Optimized down to 96 bytes

README.md

@@ -1,6 +1,6 @@
 # Print unsigned 16-bit
 
-6502 assembly code to print an unsigned 16-bit in 117 bytes ($75).
+6502 assembly code to print an unsigned 16-bit in 96 bytes ($60).
 
 
 * No zero-page usage
@@ -13,21 +13,18 @@ Copy/Paste into your favorite emulator.
 
 ```asm
 0800:A9 12 A2 34 4C 07 08 8E
-0808:7A 08 8D 7B 08 A9 00 8D
-0810:70 08 8D 71 08 8D 72 08
-0818:A2 10 F8 0E 7A 08 2E 7B
-0820:08 A0 FD B9 73 07 79 73
-0828:07 99 73 07 C8 D0 F4 CA
-0830:D0 E9 D8 A0 04 A9 B0 8D
-0838:74 08 B9 6F 08 20 53 08
-0840:88 D0 F7 8E 70 08 B9 74
-0848:08 20 ED FD C8 CC 70 08
-0850:90 F4 60 48 20 7B F8 20
-0858:5D 08 68 29 0F D0 04 E0
-0860:00 F0 0C C9 0A 90 02 69
-0868:06 69 B0 9D 74 08 E8 60
-0870:00 00 00 00 00 00 00 00
-0878:00 00 00 00 
+0808:65 08 8D 66 08 A9 00 8D
+0810:61 08 8D 62 08 8D 63 08
+0818:A2 10 F8 0E 65 08 2E 66
+0820:08 A0 FD B9 64 07 79 64
+0828:07 99 64 07 C8 D0 F4 CA
+0830:D0 E9 D8 A0 03 B9 60 08
+0838:20 44 08 88 D0 F7 8A E0
+0840:00 F0 11 60 48 20 7B F8
+0848:20 4E 08 68 29 0F D0 04
+0850:E0 00 F0 0C C9 0A 90 02
+0858:69 06 69 B0 20 ED FD E8
+0860:60 00 00 00 00 00 00 
 ```
 
 

print_uint16.s

@@ -45,25 +45,17 @@ _DoubleDabble           ;              Y=FD   Y=FE   Y=FF   Y=00
         CLD             ; X=0 = output length
 
 DecWidth
-        LDY #4          ; 6 digit output for special case of $0000
-
-        LDA #'0' + $80  ; handle special case input = $0000
-        STA _output     ; since we always print at least 1 digit
-
+        LDY #3          ; maximum 6 digits output
 BCD2Chars
         LDA _bcd-1,Y
-        JSR HexA        ; _output[0..7] = '?'
+        JSR HexA        ; print 0, 1, or 2 hex digits
         DEY
         BNE BCD2Chars
 
-        STX _len        ; output buffer len = num digits to print
+        TXA
+        CPX #0          ; Handle special case input = $0000 of no output
+        BEQ  _HaveLeadingDigit
 
-OutDigits
-        LDA _output,Y   ; always print digit in "ones" place
-        JSR COUT
-        INY
-        CPY _len
-        BCC OutDigits
 _PrintDone
         RTS
 
@@ -83,20 +75,16 @@ _HexNib
 
 _HaveLeadingDigit
         CMP #$A         ; n < 10 ?
-
         BCC _Hex2Asc
         ADC #6          ; n += 6    $A -> +6 + (C=1) = $11
 _Hex2Asc
         ADC #'0' + $80  ; inverse=remove #$80
 PutChar
-        STA _output,X
+        JSR COUT
         INX             ; X = output string length
 _HexAsciiDone
         RTS
 
-
 _bcd    ds  4   ; 6 chars for printing dec
-_len    = _bcd  ; alias
-_output ds  6   ; BCD -> 6 chars
 _temp   db  0,0