Implement LAX (absolute, X).

hainesr · Oct 28, 2020 · 4ad4244 · 4ad4244
1 parent 2578a5c
commit 4ad4244
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diff --git a/lib/mos6502/cpu_illegal_instructions.rb b/lib/mos6502/cpu_illegal_instructions.rb
@@ -119,6 +119,12 @@ def illegal_instructions
           set_nz_flags(@a)
         },
 
+        # LAX (absolute, X)
+        0xbf => lambda {
+          @a = @x = @memory.get(absolute(@x))
+          set_nz_flags(@a)
+        },
+
         # NOP (zero page, X)
         0xd4 => lambda {
           zero_page(@x)

diff --git a/test/cpu_illegal_instructions_test.rb b/test/cpu_illegal_instructions_test.rb
@@ -145,4 +145,13 @@ def test_0xb7
     assert_equal(0x80, @cpu.a)
     assert_equal(0x80, @cpu.x)
   end
+
+  # LAX (absolute, X)
+  def test_0xbf
+    @cpu.load!([0xa2, 0x01, 0xbf, 0x01, 0x06])
+    @cpu.step
+    @cpu.step
+    assert_equal(0xbf, @cpu.a)
+    assert_equal(0xbf, @cpu.x)
+  end
 end