CML (current mode logic) OCD (off chip driver)—ODT (on die termination) circuit for bidirectional data transmission

摘要

An apparatus for use as both an off chip driver (OCD) and an on die termination (ODT) circuits. A preferred embodiment comprises a control circuit (for example, control circuit 305) coupled to a dual function OCD/ODT circuit (for example, OCD/ODT circuit 330) with an enable line coupled to the control circuit. The control circuit may be used to selectively choose OCD and ODT functionality based on a value on the enable line. With the control circuit choosing OCD, the dual function OCD/ODT circuit functions as an OCD circuit, placing signals provided through the control circuit onto a transmission line. With the control circuit choosing ODT, the dual function OCD/ODT circuit becomes terminating resistors for incoming signals on a transmission line. The use of a single circuit for both OCD and ODT functions can save both integrated circuit real-estate and implementation costs due to a reduction in use of circuit elements.