digital video cassette recorder dvcr or set top box stb provides convenient management of the descrambling keys for simplicity the below description of the invention will be directed towards an implementation using a digital television dtv and a smart card including the present uart circuit fig1 depicts a system 30 for managing access to a digital television dtv 40 a smart card sc 42 is inserted into or coupled to a smart card reader 43 of the dtv 40 and an internal bus 45 interconnects dtv 40 and sc 42 thereby permitting the transfer of data therebetween the uart according to the exemplary embodiment of the present invention is preferably formed as an integral part of smart card 42 however the uart may be formed as a separate element dtv 40 can receive services from a plurality of service providers sps such as a broadcast television sp 50 a cable television sp 52 a satellite system sp 54 and an internet sp 56 conditional access organization ca 75 is not directly connected to either the service providers 50 56 or dtv 40 but deals with key management and issues key pairs which may be used to limit access to the programs transmitted by the service providers 50 56 as is well known in the art smart card 42 of the system 30 preferably includes input output terminals a processor a memory and a uart circuit in the exemplary embodiment of the present invention the uart circuit comprises a uart circuit as described above including a memory for storing a 5 byte command string and error data although the uart according to the exemplary embodiment of the present invention is preferably used in a smart card of.