Method and apparatus for graceful preemption on a digital communications link

摘要

A method and apparatus for graceful preemption on a digital communications link used for selective communication from a plurality of user devices. Link controllers are used to implement the enforcement of a protocol on the link. When a first user device is actively communicating over the link, a second user device can gracefully preempt the first user device by having a link controller transmit a preempt character. The link controllers at either end of the link each save values of a set of status variables collectively defining the status of the link controller. When the second user device relinquishes link access, the saved values are used to return the link controllers to their status at the time of preemption such that the first user device can resume communication from the point of interruption without requiring data retransmission.