Controlling power sequencing of a control unit in an input/output system

摘要

A mechanism for controlling the powering-on and powering-off of control units in a data processing system having a plurality of channels, a plurality of control units, and a communications network of links for linking the channels to the control units. Each control unit includes a power-control table for recording power-control allegiance of the control unit to the channels. Where a control unit receives a power-on command from a channel, it records the identity of the channel in its power-control table. When a channel orders a control unit to power-off, the control unit checks to see if it owes power-control allegiance to the ordering channel. If it does, the control unit deletes the identity from its power-control table. The control unit will not power-off unless its power-control table is empty, indicating that it does not owe allegiance to any other channel.