SN54HC253 SN54HC237 SN54HC21 SN54HC245-SP SN54HC244-SP SN54HC273-DIE SN54HC20-SP SN54HC20 SN54HC240 SN54HC241 SN54HC244 SN54HC245 SN54HC251 SN54HC257 SN54HC259 SN54HC27 SN54HC273 SN54HC273-SP