Implement ROR (zero page, X).

hainesr · Oct 24, 2020 · 57fbc40 · 57fbc40
1 parent 532e6bf
commit 57fbc40
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diff --git a/lib/mos6502/cpu_instructions.rb b/lib/mos6502/cpu_instructions.rb
@@ -232,6 +232,12 @@ def instructions
           @pc = branch(offset) if @status.overflow?
         },
 
+        # ROR (zero page, X)
+        0x76 => lambda {
+          address = zero_page(@x)
+          @memory.set(address, ror(@memory.get(address)))
+        },
+
         # SEI
         0x78 => lambda {
           @status.interupt_disable = true

diff --git a/test/cpu_instructions_test.rb b/test/cpu_instructions_test.rb
@@ -516,6 +516,18 @@ def test_0x70
     assert_equal(0xff, @cpu.y)
   end
 
+  def test_0x76
+    @cpu.load!([0xa9, 0x7f, 0xa2, 0xbc, 0x95, 0x70, 0x76, 0x70])
+    @cpu.step
+    @cpu.step
+    @cpu.step
+    @cpu.step
+    assert(@cpu.carry?)
+    refute(@cpu.negative?)
+    refute(@cpu.zero?)
+    assert_equal([0x3f], @cpu.dump_memory(0x2c, 1))
+  end
+
   def test_0x81
     @cpu.load!(
       [