Apparatus and method for driving a bus to a docking safe state in a dockable computer system including a docking station and a portable computer

• US 5,598,537 A
• Filed: 07/26/1994
• Issued: 01/28/1997
• Est. Priority Date: 03/25/1994
• Status: Expired due to Term

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Swanstrom, Scott, Gephardt, Douglas D.
• Primary Examiner(s): Ray, Gopal C.
• Application Number:
  US08/280,314
• Time in Patent Office: 917 Days
• Field of Search: 395/308, 395/800, 395/500, 395/822, 395/200.2, 395/200.01, 395/281-283, 361/683, 361/686, 364/708.1
• US Class Current: 710/304
• CPC Class Codes: G06F 1/1632 External expansion units, e.g. docking stations
• CPC Class Codes: G06F 13/364 using independent requests or grants, e.g. using separated request and grant lines
• CPC Class Codes: G06F 13/4036 and deadlock prevention
• CPC Class Codes: G06F 13/4072 Drivers or receivers G06F13/4086 takes precedence; for multistate logic circuits H03K19/0002
• CPC Class Codes: G06F 13/4081 Live connection to bus, e.g. hot-plugging current or voltage limitation during live insertion H02H9/004

Abstract

In a dockable computer system capable of hot docking or warm docking, a docking safe circuit drives the bus of the portable computer and docking station to a docking safe state in response to a DOCK signal. The DOCK signal may be a notice signal indicative of a change of state from the undocked state to the docked state or from the docked state to the undocked state. The notice signal may be provided from software, a user-actuated switch or an infrared signal. Preferably, the docking safe state or dockable state is a state in which: the ground conductors of the buses are referenced to a common ground potential; the buses are "quiet" or non-transitioning; the bidirectional terminals on the bus of the portable computer are set to an output state; the bidirectional terminals of the bus of the docking station are set to an input state; and the signaling levels of the buses have the same voltage potential. Preferably, the present invention is implemented on a peripheral component interconnect (PCI) bus.

Claims

1. A portable computer in a dockable computer system for assuming at least two states, a docked state and an undocked state, said dockable computer system including a host station, said dockable computer system being in said docked state when said portable computer is operatively associated with said host station and being in said undocked state when said portable computer is physically separate from said host station, said portable computer comprising:

a computer bus;

a processor coupled to said computer bus;

a docking safe circuit communicating with said computer bus, said docking safe circuit including a dock input, said dock safe circuit driving said computer bus to a docking safe state in response to a DOCK signal on said dock input, wherein said portable computer includes a plurality of bidirectional terminals coupled to said computer bus, and said docking safe state includes setting said bidirectional terminals coupled to said computer bus to an output state before said dockable computer system attains said docked state or said undocked state, and wherein said host station includes a host bus said host station including a plurality bidirectional terminals coupled to said host bus, and said docking safe state includes setting said bidirectional terminals coupled to said host bus to an input state before said dockable computer system attains said docked state or said undocked state, and wherein said docking safe state includes quieting said computer bus before said dockable computer system attains said docked state or said undocked state; and

a dock circuit communicating with said docking safe circuit, said dock circuit providing said DOCK signal in response to said dockable computer system changing states, said dock circuit sensing when said portable computer is physically separate from said host station and when said portable computer is operatively associated with said host station to generate said dock signal before said dockable computer system attains said docked state or said undocked state whereby said portable computer remains powered on without suspending operation of said processor during the transition from said undocked state to said docked state.

2. The portable computer of claim 1, wherein said portable computer includes a portable connector coupled to said computer bus and said host station includes a host connector coupled to a host bus, wherein said dockable computer system includes a ground reference station communicating with said portable computer and said host connector for ensuring said portable computer and said host station have a common ground reference in accordance with said docking safe state.

3. The portable computer of claim 2, wherein said host connector and said portable connector are configured so that said ground reference circuit communicates with said portable connector and said host connector engaged before first conductors associated with said host connector communicate with second conductors associated with said portable connector.

4. The portable computer of claim 1, wherein said dock safe circuit further comprises a bus isolation circuit having inputs coupled to said computer bus and outputs, said bus isolation circuit driving said outputs to a high impedance state in response to said DOCK signal.

5. The portable computer of claim 4, wherein said bus isolation circuit further quiets said computer bus in response to the dock signal.

6. The portable computer of claim 4 wherein said portable computer includes a connector bus between said bus isolation circuit and a connector, said bus isolation circuit being coupled between said connector bus and said computer bus, said connector bus being directly coupled to the connector.

7. The portable computer of claim 6 wherein the bus isolation circuit includes tri-state buffers and a signal keeper circuit including back-to-back inverters, the back-to-back inverters maintaining the current pin status on terminals coupled to said computer bus, wherein the back-back inverters can be overdriven by a plurality of devices coupled to the computer bus.

8. The portable computer of claim 1, wherein said computer bus is a PCI bus.

9. A method of docking or undocking a portable computer and a host station of a dockable computer system, said portable computer having a processing unit coupled to a computer bus and said host station having a host bus, said dockable computer system including a dock circuit for generating a DOCK signal in response to docking or undocking said portable computer, said computer bus being physically, and electrically coupled with said host bus when said portable computer is docked with said host station, said docking circuit sensing when said portable computer is about to be docked or undocked with said host station and determining when said portable computer is docking or undocking to generate said DOCK signal, said method comprising the steps of:

receiving said DOCK signal provided by said dock circuit;

driving said computer bus to a docking safe state in response to said dock signal by placing a plurality of bidirectional terminals coupled to said computer bus to an output state; and

coupling or uncoupling said host bus and said computer bus, whereby said portable computer remains powered on without suspending operation of said processing unit when said portable computer is coupled with or uncoupled from said host station.

10. The method of claim 9, further comprising the step of:

driving said host bus to a second docking safe state by placing a plurality of bidirectional terminals coupled to the host bus to an input state.

11. The method of claim 10, wherein said second docking safe state includes quieting said host bus.

12. The method of claim 11, wherein said portable computer includes signal keepers for maintaining said computer bus in said docking safe state.

13. The method of claim 9, wherein said docking safe state includes quieting said computer bus.

14. A computer operated in an undocked state or a docked state with a station having a station bus, said computer including a computer bus, a connector bus and a computer connector coupled to said connector bus, said station including a station connector coupled to said station bus, said computer connector being coupled to said station connector when said computer is operable in said docked state, said computer connector being physically separate from said station connector when said computer is operable in said undocked state, said computer comprising:

a CPU for physical electrical communication with said computer bus; and

a bus isolation circuit coupled between said computer bus and said connector bus, said connector bus being coupled between said bus isolation circuit and said computer connector, said bus isolation circuit isolating said computer bus to place said computer bus in a docking safe state when said computer changes states, said bus isolation circuit bringing said connector bus to a high impedance state to isolate said computer bus from said station bus in response to a dock signal indicating when said computer is about to change states, whereby said CPU remains powered on and said CPU remains operational when said computer changes states; and

a dock sense circuit for sensing when said computer is about to change states and determines when said computer connector is about to be coupled to said station connector or when said computer connector is about to be disconnected from said station connector to generate said dock signal, said dock sense circuit generating said dock signal in response to said computer being about to change states.

15. The computer of claim 14, wherein said bus isolation circuit receives a notice signal indicating that said computer is about to change states and said bus isolation circuit drives said computer connector to a docking safe state in response to said notice signal.

16. The computer of claim 15, wherein said computer connector includes a ground pin interface.

17. The computer of claim 15, wherein said bus isolation circuit drives said computer connector to a high impedance state when said bus isolation circuit isolates said bus of said computer.

18. The computer of claim 14, wherein said bus isolation circuit includes FIFO buffers and state machines.

19. The computer of claim 14, wherein said bus isolation circuit is an in-line device coupled between said bus of said computer and said computer connector.

20. A dockable computer system comprising;

a host computer station, including a processor and a station bus;

a mobile computer unit including a unit bus, wherein said system is capable of residing in at least two distinct states, a docked state in which said unit is operatively associated with said station and an undocked state in which said unit is physically separate from said station;

a docking safe circuit coupled to said unit bus, said docking safe circuit driving said unit bus to a docking safe state in response to a dock signal before said system changes from said undocked state to a docked state or from said docked state to said undocked state, said docking safe state including setting a plurality of bidirectional terminals coupled to said unit bus to an output state, setting a plurality of bidirectional terminals coupled to said station bus to an input state, setting the logic high signal level of said station bus to the logic high signal level of said unit bus, and referencing ground conductors on said station bus and the unit bus to the same ground potential, whereby said mobile computer unit remains powered on without suspending said processor when said mobile computer unit is docked with said host computer station; and

a dock sense circuit for sensing when said dockable computer system is about to change states, said dock sense circuit determining when said unit is about to be operatively associated with said station or when said unit is about to be physically separate from said station to generate said dock signal in response to said dockable computer system being about to change states.