cpu: add JAM instructions

1 files changed, 35 insertions, 1 deletions

diff --git a/tests/cpu_test.go b/tests/cpu_test.go
index 87743b1..269f9ee 100644
--- a/tests/cpu_test.go
+++ b/tests/cpu_test.go
@@ -232,6 +232,40 @@ func TestUnimplementedOpcodePanics(t *testing.T) {
 			t.Fatalf("expected panic for illegal opcode")
 		}
 	}()
-	c, _ := newTestCPU([]uint8{0x02})
+	c, _ := newTestCPU([]uint8{0x8B})
 	c.Step()
 }
+
+func TestJamStopsCPU(t *testing.T) {
+	c, _ := newTestCPU([]uint8{0xA9, 0x42, 0x02, 0xEA})
+	c.Step()
+	c.Step()
+	if !c.Jammed {
+		t.Fatal("Jammed = false, want true")
+	}
+	if c.PC != 0x8002 {
+		t.Fatalf("PC = 0x%04X, want 0x8002", c.PC)
+	}
+	for i := 0; i < 3; i++ {
+		if cycles := c.Step(); cycles != 1 {
+			t.Fatalf("cycles = %d, want 1", cycles)
+		}
+	}
+	if c.PC != 0x8002 || c.A != 0x42 {
+		t.Fatalf("PC = 0x%04X, A = 0x%02X; want 0x8002, 0x42", c.PC, c.A)
+	}
+}
+
+func TestJammedIgnoresInterruptsUntilReset(t *testing.T) {
+	c, bus := newTestCPU([]uint8{0x02})
+	bus.mem[0xFFFA], bus.mem[0xFFFB] = 0x00, 0x90
+	c.Step()
+	c.NMI()
+	if c.PC != 0x8000 {
+		t.Fatalf("PC after NMI = 0x%04X, want 0x8000", c.PC)
+	}
+	c.Reset()
+	if c.Jammed {
+		t.Fatal("Jammed = true after Reset, want false")
+	}
+}