Apparatus and method for testing the ability of a pair of serial data transceivers to transmit serial data at one frequency and to receive serial data at another frequency

Abstract

An apparatus and method are presented for testing the ability of a pair of serial data transceivers to transmit serial data at one frequency and to receive serial data at another frequency. A serial communication device of the present invention includes a first and second serial data transceivers and a multiplexer formed upon a monolithic semiconductor substrate. Each serial data transceiver includes a receiver and a transmitter which transmits serial data in response to a clock signal. The second serial data transceiver is coupled to receive a reference clock signal. The multiplexer facilitates testing, and is coupled to the first serial data transceiver. The multiplexer receives the reference clock signal, a test clock signal, and a test signal, and provides either the reference clock signal or the test clock signal to the first transceiver dependent upon the test signal. The reference and test clock signals have different frequencies. The multiplexer provides the reference clock signal to the first transceiver when the test signal is deasserted, and provides the test clock signal to the first transceiver when the test signal is asserted. During testing, the output of the transmitter of one transceiver is coupled to the input of the receiver of the other transceiver, and the test signal is asserted. Each receiver produces parallel output test data. A match between the two sets of parallel output test data and the parallel input test data demonstrates the abilities of both transceivers to transmit and receive serial data at different frequencies.