Abstract: A keyboard interface for a data processing system in which a keyboard and a data processor unit are connected through a single clock line for transmitting a clock signal from the keyboard and a single data line for transmitting a serial bit frame having a serial scan code identifying a depressed key in synchronism with the clock signal. The interface uses an error detection and retransmission procedure to correct errors due to noise pulses which are induced on the clock line as by electrostatic discharge and give rise to extra data sampling. The data processing system returns a status signal acknowledging the receipt of a frame to the keyboard via the data line immediately after the number of sampled bits received reaches the predetermined number of bits of a frame. The keyboard checks whether the status signal has been returned after the completion of transmission of a frame and, if not, the same serial scan code is retransmitted.