Merge pull request #18 from fedex81/bcd-fixes

68k: fix abcd/sbcd -(aN),-(aN)
tonyheadford · Nov 1, 2022 · e6b6f3a · e6b6f3a
2 parents c5e739c + d86e481
commit e6b6f3a
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Showing 4 changed files with 37 additions and 2 deletions.
diff --git a/src/m68k/cpu/instructions/ABCD.java b/src/m68k/cpu/instructions/ABCD.java
@@ -100,8 +100,8 @@ protected final int abcd_ar(int opcode) {
 		int sreg = (opcode & 0x07);
 		int dreg = (opcode >> 9) & 0x07;
 		cpu.decrementAddrRegister(sreg, 1);
-		cpu.decrementAddrRegister(dreg, 1);
 		int s = cpu.readMemoryByte(cpu.getAddrRegisterLong(sreg));
+		cpu.decrementAddrRegister(dreg, 1);
 		int d = cpu.readMemoryByte(cpu.getAddrRegisterLong(dreg));
 
 		int result = calc(cpu, s, d);

diff --git a/src/m68k/cpu/instructions/SBCD.java b/src/m68k/cpu/instructions/SBCD.java
@@ -100,8 +100,8 @@ protected final int sbcd_ar(int opcode) {
 		int sreg = (opcode & 0x07);
 		int dreg = (opcode >> 9) & 0x07;
 		cpu.decrementAddrRegister(sreg, 1);
-		cpu.decrementAddrRegister(dreg, 1);
 		int s = cpu.readMemoryByte(cpu.getAddrRegisterLong(sreg));
+		cpu.decrementAddrRegister(dreg, 1);
 		int d = cpu.readMemoryByte(cpu.getAddrRegisterLong(dreg));
 
 		int result = calc(cpu, s, d);

diff --git a/test/miggy/cpu/instructions/bcd/ABCDTest.java b/test/miggy/cpu/instructions/bcd/ABCDTest.java
@@ -54,4 +54,22 @@ public void testMem() {
         assertFalse("Check V 2", SystemModel.CPU.isSet(CpuFlag.V));
         assertFalse("Check C 2", SystemModel.CPU.isSet(CpuFlag.C));
     }
+
+    public void testMem2() {
+        setInstruction(0xc108);    //abcd -(a0),-(a0)
+        SystemModel.CPU.setAddrRegister(0, codebase + 100);
+        SystemModel.MEM.poke(codebase + 98, 0x2316, Size.Word);
+
+        SystemModel.CPU.setCCR((byte) 0);
+
+        int time = SystemModel.CPU.execute();
+
+        //23+16 = 39
+        assertEquals("Check result", 0x3916, SystemModel.MEM.peek(codebase + 98, Size.Word));
+        assertFalse("Check X", SystemModel.CPU.isSet(CpuFlag.X));
+        assertFalse("Check N", SystemModel.CPU.isSet(CpuFlag.N));
+        assertFalse("Check Z", SystemModel.CPU.isSet(CpuFlag.Z));
+        assertFalse("Check V", SystemModel.CPU.isSet(CpuFlag.V));
+        assertFalse("Check C", SystemModel.CPU.isSet(CpuFlag.C));
+    }
 }
diff --git a/test/miggy/cpu/instructions/bcd/SBCDTest.java b/test/miggy/cpu/instructions/bcd/SBCDTest.java
@@ -53,4 +53,21 @@ public void testMem() {
         assertFalse("Check V 2", SystemModel.CPU.isSet(CpuFlag.V));
         assertFalse("Check C 2", SystemModel.CPU.isSet(CpuFlag.C));
     }
+
+    public void testMem2() {
+        setInstruction(0x8108);    //sbcd -(a0),-(a0)
+        SystemModel.CPU.setAddrRegister(0, codebase + 100);
+        SystemModel.MEM.poke(codebase + 98, 0x3916, Size.Word);
+        SystemModel.CPU.setCCR((byte) 0);
+
+        int time = SystemModel.CPU.execute();
+
+        //39-16 = 23
+        assertEquals("Check result", 0x2316, SystemModel.MEM.peek(codebase + 98, Size.Word));
+        assertFalse("Check X", SystemModel.CPU.isSet(CpuFlag.X));
+        assertFalse("Check N", SystemModel.CPU.isSet(CpuFlag.N));
+        assertFalse("Check Z", SystemModel.CPU.isSet(CpuFlag.Z));
+        assertFalse("Check V", SystemModel.CPU.isSet(CpuFlag.V));
+        assertFalse("Check C", SystemModel.CPU.isSet(CpuFlag.C));
+    }
 }