An apparatus includes a first interface having a communication channel through which data is transmitted to or received from a target device and a first control register that is configured to control, based at least in part on its contents, transmission or reception of data through the communication channel. The apparatus also includes a second interface having a second control register that is configured to control, based at least in part on its contents, transmission or reception of data through the communication channel. A circuit in the apparatus harmonizes the contents of the first control register and the second control register, such that an external controller can control transmission or reception of data through the communication channel by providing control data in a first format to the first control register or by providing alternate control data in a second different format to the second control register.