diff --git a/OSBindings/Mac/Clock SignalTests/68000ComparativeTests.mm b/OSBindings/Mac/Clock SignalTests/68000ComparativeTests.mm
index 83947c847..019381314 100644
--- a/OSBindings/Mac/Clock SignalTests/68000ComparativeTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/68000ComparativeTests.mm	
@@ -187,10 +187,10 @@ struct TestProcessor: public CPU::MC68000Mk2::BusHandler {
 //		@"rtr.json",
 //		@"rts.json",
 		@"swap.json",
-//		@"tas.json",
+		@"tas.json",
 //		@"tst.json",
 	]];
-//	_testSet = [NSSet setWithArray:@[@"PEA 0038"]];
+//	_testSet = [NSSet setWithArray:@[@"TAS 4ac0"]];
 }
 
 - (void)testAll {
diff --git a/Processors/68000Mk2/Implementation/68000Mk2Implementation.hpp b/Processors/68000Mk2/Implementation/68000Mk2Implementation.hpp
index 429cbb9fa..4b2eb5bc1 100644
--- a/Processors/68000Mk2/Implementation/68000Mk2Implementation.hpp
+++ b/Processors/68000Mk2/Implementation/68000Mk2Implementation.hpp
@@ -165,6 +165,7 @@ enum ExecutionState: int {
 	MULU_MULS,
 	LEA,
 	PEA,
+	TAS,
 };
 
 // MARK: - The state machine.
@@ -714,6 +715,20 @@ void Processor<BusHandler, dtack_is_implicit, permit_overrun, signal_will_perfor
 					MoveToStateSpecific(CalcEffectiveAddress);
 				});
 
+				StdCASE(TAS, {
+					// TAS uses a special atomic bus cycle for memory accesses,
+					// but is also available as DataRegisterDirect, with no
+					// memory access whatsoever. So segue elsewhere here only
+					// for the other cases.
+					if(instruction_.mode(0) != Mode::DataRegisterDirect) {
+						post_ea_state_ = TAS;
+						next_operand_ = 0;
+						MoveToStateSpecific(CalcEffectiveAddress);
+					}
+
+					perform_state_ = Perform_np;
+				});
+
 				default:
 					assert(false);
 			}
@@ -1902,6 +1917,17 @@ void Processor<BusHandler, dtack_is_implicit, permit_overrun, signal_will_perfor
 			Prefetch();
 		MoveToStateSpecific(Decode);
 
+		//
+		// TAS
+		//
+		BeginState(TAS):
+
+			// TODO: use the specialised TAS bus cycle; five parts.
+//			PerformBusOperation
+
+			Prefetch();
+		MoveToStateSpecific(Decode);
+
 		//
 		// Various states TODO.
 		//
@@ -2019,6 +2045,16 @@ template <bool use_current_instruction_pc> void ProcessorBase::raise_exception(i
 	exception_vector_ = vector;
 }
 
+inline void ProcessorBase::tas(Preinstruction instruction, uint32_t) {
+	// This will be reached only if addressing mode is Dn.
+	const uint8_t value = registers_[instruction.reg(0)].b;
+	registers_[instruction.reg(0)].b |= 0x80;
+
+	status_.overflow_flag = status_.carry_flag = 0;
+	status_.zero_result = value;
+	status_.negative_flag = value & 0x80;
+}
+
 // MARK: - External state.
 
 template <class BusHandler, bool dtack_is_implicit, bool permit_overrun, bool signal_will_perform>
diff --git a/Processors/68000Mk2/Implementation/68000Mk2Storage.hpp b/Processors/68000Mk2/Implementation/68000Mk2Storage.hpp
index 8e93907da..706e27c4d 100644
--- a/Processors/68000Mk2/Implementation/68000Mk2Storage.hpp
+++ b/Processors/68000Mk2/Implementation/68000Mk2Storage.hpp
@@ -143,7 +143,7 @@ struct ProcessorBase: public InstructionSet::M68k::NullFlowController {
 	inline void unlink(uint32_t &) {}				//
 	inline void move_to_usp(uint32_t) {}			//
 	inline void move_from_usp(uint32_t &) {}		//
-	inline void tas(Preinstruction, uint32_t) {}	//
+	inline void tas(Preinstruction, uint32_t);
 	template <bool use_current_instruction_pc = true> void raise_exception(int);
 
 	// These aren't implemented because the specific details of the implementation