Dual PCI bridge docking

Details Dual PCI bridge docking Dual PCI bridge docking

1997-09-09

2001-02-27

Wiley, David A. (Department: 2781)

Electrical computers and digital data processing systems: input/

Intrasystem connection

Bus access regulation

C710S120000

Reexamination Certificate

active

06195718

ABSTRACT:

BACKGROUND OF THE INVENTION
Computers have been designed with accessible bus connectors that provide external electrical connections to their buses. This configuration is most common in portable and specifically notebook-size computers and is used in two scenarios. The bus connector may be used to connect the portable computer to a non-portable docking station that many times allows connection to a larger display and a full size keyboard. In other implementations, the bus connector is adapted to be connected to somewhat portable dock units that can contain hard drives, CD ROMS, and power supplies. Compatible dock units are available that have larger battery power supplies, CD ROMS, and other capabilities for multimedia functions, for example.
One issue that arises when providing this docking capability is how to handle the physical electrical mating between the computer, or primary unit, and the dock unit. Glitches or anomalous voltages will arise on the primary bus when the primary bus makes electrical contact with the corresponding connector on the dock unit's bus extension. Such glitches can cause the primary unit to hang or become inoperable, requiring rebooting.
One solution to handling the docking and the resulting glitches on the bus is to render docking illegal when the primary unit is operational. This solution solves the problem of compensating for the glitches, but is somewhat unacceptable to most users. Another solution is to provide buffers between the primary bus and the primary unit's bus extension. During operation, these buffers act as relay agents that simply pass-on valid bus activity between the primary bus and extension in the dock unit. During docking, however, they prevent the glitches from appearing on the primary unit's bus and, thus, insulate the primary unit. The problem with the buffer solution is two-fold. The buffers: 1) add expense to the primary unit since they represent an additional hardware system; and 2) slow transactions between the primary bus and the dock unit's bus extension.
Another approach is to generate a dock request signal just prior to the physical connection between the primary unit's bus conductors and those of the dock unit; the primary unit electrically floats the primary bus in response to receiving this request signal. The solution, while allowing hot docking or docking while the primary unit is operational, avoids the delay and costs associated with the hardware buffers. The problem, however, is that established protocols do not allow the docking of a second dock unit to dock/primary unit pairs.
SUMMARY OF THE INVENTION
The present invention concerns a multiple docking system that allows multiple dock units to be connected to the bus of a primary unit. This is accomplished using multiple bridges between the primary bus of the primary unit and secondary buses in each of the dock units. Importantly, the system allows for hot docking or docking of the multiple dock units to the primary unit while the primary unit is operational by notifying the dock units that docking is taking place and relaying the information to the primary unit.
In general, according to one aspect, the invention features a multiple dock docking system for a computer system comprising a primary unit having a microprocessor and at least two dock units having bus devices addressable by the microprocessor. The docking system comprises a primary bus of the microprocessor that is accessible to the dock units via a bus connector on the primary unit. Bridges in the dock units, supporting respective secondary buses, electrically interface with the primary bus through the primary unit bus connector.
In one embodiment, the first one of the dock units connects to the primary unit bus connector and a second dock unit connects to a dock unit bus connector on the first dock unit. A primary bus extension passes through the first dock unit from the primary unit bus connector to the dock unit bus connector.
In an alternative embodiment, the bridge of the second dock connects to an auxiliary or secondary bus serviced by a bridge of the first dock unit. As a result, the buses of the dock units are serialized with respect to each other.
In either case, docking a second dock unit to the first dock unit generates a dock signal to the bridge of the first dock unit. The bridge concludes bus activity and sends a float request signal to the primary unit. The primary unit responds with a float grant signal, at which time the bridge floats its secondary bus and the primary unit floats the primary bus.
The invention also relates to an inventive bridge that supports the hot docking of a second dock unit. Specifically, the bridge in the first dock unit is capable of receiving the dock signal, which causes the bridge to complete bus transactions between the primary bus and the first dock unit's secondary bus. The bridge also generates a float request signal to the primary unit and then floats the secondary bus only after receiving a float grant signal back.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.


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patent: 0674275 (1995-09-01), None
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Hot docking PCI-to-PCI has link to ISA past,Electronic Engineering, vol. 67, No. 827, Nov. 1995, p. 14.
PCI System Architecture,Shanley & Anderson, Nov. 1995, pp. 381-386, figures 19-1, 19-2.

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