[crabemu-svn-commits] SF.net SVN: crabemu:[229] trunk/CrabEmu

[<ljs...@us...>]

Revision: 229
          http://sourceforge.net/p/crabemu/code/229
Author:   ljsebald
Date:     2014-06-29 19:20:54 +0000 (Sun, 29 Jun 2014)
Log Message:
-----------
Add BCD support to ARR in Crab6502.

Modified Paths:
--------------
    trunk/CrabEmu/CHANGELOG
    trunk/CrabEmu/src/cpu/Crab6502/Crab6502ops.h

Modified: trunk/CrabEmu/CHANGELOG
===================================================================
--- trunk/CrabEmu/CHANGELOG	2014-06-27 20:56:51 UTC (rev 228)
+++ trunk/CrabEmu/CHANGELOG	2014-06-29 19:20:54 UTC (rev 229)
@@ -6,6 +6,7 @@
 
 6502 Core:
 - Implemented BCD mode for the ADC and SBC instructions.
+- Implemented BCD mode for the ARR undocumented instruction.
 
 SMS/TMS9918A VDP Core:
 - Fixed an issue where the sms_vdp_update_cache would read memory outside of the

Modified: trunk/CrabEmu/src/cpu/Crab6502/Crab6502ops.h
===================================================================
--- trunk/CrabEmu/src/cpu/Crab6502/Crab6502ops.h	2014-06-27 20:56:51 UTC (rev 228)
+++ trunk/CrabEmu/src/cpu/Crab6502/Crab6502ops.h	2014-06-29 19:20:54 UTC (rev 229)
@@ -218,9 +218,30 @@
     case 0x6B:  /* (U) ARR imm */
         FETCH_ARG8(_tmp);
 #ifndef CRAB6502_NO_DECIMAL
+        /* Yup... this makes about... zero sense. */
         if(cpu->p & 0x08) {
-            /* XXXX: Support BCD mode */
-            assert(0);
+            uint8 _al, _ah;
+
+            _tmp32 = _tmp = cpu->a & _tmp;
+            _ah = _tmp >> 4;
+            _al = _tmp & 0x0F;
+            _tmp = (_tmp >> 1) | ((cpu->p & 0x01) << 7);
+
+            /* Set all the flags except for C. */
+            cpu->p = (cpu->p & 0x3C) | ZNtable[_tmp] | ((_tmp32 ^ _tmp) & 0x40);
+
+            /* BCD adjust (sorta) the low order bits. */
+            if(_al + (_al & 0x01) > 5)
+                _tmp = (_tmp & 0xf0) | ((_tmp + 6) & 0x0F);
+
+            /* BCD adjust (sorta) the high order bits, and set C if needed. */
+            if(_ah + (_ah & 0x01) > 5) {
+                cpu->p |= 0x01;
+                _tmp = (_tmp + 0x60);
+            }
+
+            cpu->a = _tmp;
+            cycles_done += 2;
             break;
         }
 #endif

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