US Patent 10067189 Input/output path testing and characterization using scan chains

Disclosed circuitry includes input-output pads, receive flip-flops, and transmit flip-flops coupled to the input-output pads. Data path control circuitry is coupled to data path control flip-flops, the receive flip-flops and the transmit flip-flops. The data path control circuitry is configured to selectably couple the receive flip-flops and the transmit flip-flops to the input-output pads in response to states of the data path control flip-flops. Clock control circuitry is coupled to clock control flip-flops, the receive flip-flops and the transmit flip-flops. The clock control circuitry is configured to selectably apply one of multiple clock signals to the receive flip-flops and the transmit flip-flops in response to states of the clock control flip-flops. A first scan chain is coupled to the clock control flip-flops and the data path control flip-flops. A second scan chain is coupled to the receive flip-flops and the transmit flip-flops.