From b505f7a50da6b8a513ed93c6065258a7c7198b14 Mon Sep 17 00:00:00 2001
From: Preston Skupinski <skupinsk@cse.msu.edu>
Date: Sat, 3 Sep 2011 22:07:44 -0400
Subject: [PATCH] handle the carry bit properly when in decimal mode for adc

---
 cpu.js        |  8 ++++++--
 test/tests.js | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/cpu.js b/cpu.js
index 051fb8a..aafbf01 100644
--- a/cpu.js
+++ b/cpu.js
@@ -3620,11 +3620,13 @@ var ADC_const = {
         ones = bytes[0] & 0x0f;
         tens = bytes[0] >>4;
         var dec_arg = (tens*10)+ones;
-        var result = dec_a + dec_arg;
+        var result = dec_a + dec_arg + cpu.p.c;
         // Check for decimal overflow.
         if(result>99) {
           result -= 99;
           cpu.p.c = 1; 
+        } else {
+          cpu.p.c = 0;
         }
         var digits = result.toString(10).split("");
         var i = 0;
@@ -3667,11 +3669,13 @@ var ADC_const = {
         hundreds = (argument >> 8) & 0xf;
         thousands = (argument >> 12) & 0xf;
         var dec_arg = (thousands*1000)+(hundreds*100)+(tens*10)+ones;
-        var result = dec_a + dec_arg;
+        var result = dec_a + dec_arg + cpu.p.c;
         // Check for decimal overflow.
         if(result>9999) {
           result -= 9999;
           cpu.p.c = 1; 
+        } else {
+          cpu.p.c = 0;
         }
         var digits = result.toString(10).split("");
         var i = 0;
diff --git a/test/tests.js b/test/tests.js
index 99b7dc7..26854af 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -648,6 +648,23 @@ function test_adc() {
     equals(cpu.p.e, 0, "The hidden e flag of the p status register should "+
                        "be 0 for native mode.");
   });
+  test("Test that ADC handles decimal mode with legal BCD numbers in 8-bit "+
+       "memory/accumulator mode with double digit numbers with the carry "+
+       "bit set", function() {
+    var cpu = new CPU_65816();
+    cpu.execute("18fb38f8a9156926");
+    equals(cpu.r.a, 0x42, "0x15 + 0x26 should result in 0x42 with decimal "+
+                          "mode on and with 8-bit memory/accumulator mode "+
+                          "and the carry bit set.");
+    equals(cpu.p.c, 0, "The carry flag of the p status register should be "+
+                       "clear after no decimal overflow.");
+    equals(cpu.p.d, 1, "Decimal mode should be set to 1 in the p status "+
+                       "register.");
+    equals(cpu.p.m, 1, "The m flag of the p status register should be 1 for "+
+                       "8-bit memory/accumulator mode.");
+    equals(cpu.p.e, 0, "The hidden e flag of the p status register should "+
+                       "be 0 for native mode.");
+  });
   test("Test that ADC handles decimal mode with legal BCD numbers in 8-bit "+
        "memory/accumulator mode when adding two numbers that cause an "+
        "overflow.", function() {
@@ -715,6 +732,23 @@ function test_adc() {
     equals(cpu.p.e, 0, "The hidden e flag of the p status register should "+
                        "be 0 for native mode.");
   });
+  test("Test that ADC handles decimal mode with legal BCD numbers in 16-bit "+
+       "memory/accumulator mode when adding two four digit numbers with the "+
+       "carry bit set.", function() {
+    var cpu = new CPU_65816();
+    cpu.execute("18fb38f8c220a90110699939");
+    equals(cpu.r.a, 0x5001, "0x1001 + 0x3999 should result in 0x5001 with "+
+                            "decimal mode on and with 16-bit "+
+                            "memory/accumulator mode and the carry flag set.");
+    equals(cpu.p.c, 0, "The carry flag of the p status register should be "+
+                       "clear after no decimal overflow.");
+    equals(cpu.p.d, 1, "Decimal mode should be set to 1 in the p status "+
+                       "register.");
+    equals(cpu.p.m, 0, "The m flag of the p status register should be 0 for "+
+                       "16-bit memory/accumulator mode.");
+    equals(cpu.p.e, 0, "The hidden e flag of the p status register should "+
+                       "be 0 for native mode.");
+  });
 }
 
 function test_branching() {