National Semiconductor Corporation

Pranay D Shah

Kenneth C Ma

John D Kenny

Kenneth J Kotlowski

Jeffrey A Hawkey

A secondary bus controller allows for hot insertion and ejection of devices from the secondary bus without ceasing operations or halting software in the host computer. When a device is to be inserted a signal is sent to the secondary bus controller. The secondary bus controller suspends operation of the secondary bus, placing devices on the secondary bus in stasis. An interrupt handler reconfigures the system for the newly inserted card once it has been inserted. Attempts to access devices on the secondary bus during the insertion process may be met with a retry signal until insertion is complete. The ejection process follows similar steps, isolating and suspending operations on the secondary bus and triggering an interrupt routine in the host processor to reconfigure the system. The host processor and primary busses, along with the secondary bus controller remain active throughout the insertion or ejection processes. Thus, applications running on the host computer need not be terminated during insertion or ejection. The present invention has particular application to network server computer systems.

Method and apparatus to enable insertion/ejection of a device in a

Hot-insertion/removal, herein used interchangeably with hot-docking/undocking, would enable the connection or disconnection of a fully powered bus to an expansion device with no damage or data loss to either device. Previous docking solutions typically require the docking bus to be placed into a power-off or power-managed state, which means the user would have to consciously place the system into a power-off or power-managed state before an insertion or removal could occur. The hot-docking/undocking invention is completely transparent to the end user, so it would provide tremendous flexibility and seamless insertions and removals. Hot-docking/undocking is composed of three elements: a detection of a docking/undocking situation; a placement of the docking bus into a static state; and a system reconfiguration. The present invention places the docking bus into an static state through the use of a special handshaking protocol and clock and reset signals on the expansion device. The entire mechanism can be applied in both the insertion and removal of a power-on bus to and from an expansion device.

Method and apparatus to enable docking/undocking of a powered-on bus to

A bridge and a method for interfacing a plurality of buses with the bridge provides electrical isolation between the buses but is transparent so that the plurality of buses is viewed by software as a single logical bridge. Transaction cycles initiated on one bus are reflected on the other bus. A speculative start of a transaction cycle on a secondary bus immediately after the transaction cycle has been started on the first bus provides a significant savings in time to complete transactions in which the target of the transaction is on the secondary bus.

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San Jose, CA, United States of America

Pranay D Shah