Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus expansion or extension
Reexamination Certificate
1999-10-15
2003-02-11
Myers, Paul R. (Department: 2781)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus expansion or extension
Reexamination Certificate
active
06519669
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the connection of components in computer systems and more particularly to an apparatus and method for docking/undocking control for docking and undocking a peripheral device while a computer system is in operation without affecting the operation of a bus.
BACKGROUND OF THE INVENTION
In a personal computer system, a PCI (Peripheral Component Interconnect) bus, an ISA (Industry Standard Architecture) bus, an EISA (Extended Industry Standard Architecture) bus, and an MC (Micro Channel) bus, etc., are employed as paths of data transfer among devices such as various peripheral devices. Among them, the PCI bus was proposed by Intel Corporation in 1993 and recently replacing other buses with an extended bus of a type which allows relatively high speed data transfer by a burst mode (bus width 32/64 bits, maximum operation frequency 33/66 MHz, maximum data transfer rate 132/264 MBps). The details of the PCI bus are prescribed in the PCI Local Bus Specification Rev.2.1, PCI Special Interest Group publicized by Intel Corporation.
In a notebook type personal computer (hereinafter simply referred to as a “computer”), the size and the weight are restricted due to the importance of portability; and, it is not basically permitted to add an expansion board to a mother board to enhance functions as have been done conventionally. Accordingly, an expansion slot is provided on a panel surface of a computer housing to allow an adapter card having a RAM and communication function to be selectively attached. Further in order to use the computer alone when it is carried around and allow it to be used with a function approximately similar to a desk top computer when it is used in an office, a docking station is made available which is provided with a hard disk and an expansion slot and to which a computer unit is detachably mounted.
It is convenient for a user to connect and disconnect an adapter card and a docking station to and from a computer unit without interrupting the power source of the computer. However, because a bus line is normally shared by a plurality of devices, if a computer system is mounted to the docking station and one attempts to connect busses to each other without taking a bus cycle into consideration, the load of the bus line may abruptly change, generating a noise which may cause a malfunction of the bus cycle and a disruption of operation of the system.
In order to prevent this, a hot docking/undocking technology is developed for docking and undocking without interrupting the power source of a computer. PUPA 10-187304 discloses a technology of hot docking/undocking an operating computer to and from a docking station which does not support a hot docking/undocking interface. As shown in the schematic block diagram of
FIG. 18
, this technology provides a bus switch
617
in a PCI bus line
619
of a computer
611
and a DC bridge
623
on a PCI bus line
625
of a docking station
613
. When it is detected that a computer is mounted to the docking station with the bus switch
617
being open, a PCI-ISA bridge
627
, which is a bus master of the PCI bridge, acquires ownership of the bus and generates a dummy bus cycle such as an I/O read or I/O write on the PCI bus targeting a host-PCI bridge
629
.
The host-PCI bridge
629
controls the bus switch
617
to close it while the PCI bus line
619
is in the dummy bus cycle state and to connect the PCI bus line
625
of the docking station to the PCI bus line
619
. Because the dummy bus cycle is not used as a regular read/write, the operation of the computer is not affected even if the waveform of the bus cycle is disturbed at the time when the bus switch
617
is closed. However, it is necessary in this technology to provide a new PCI device which can acquire ownership of a bus for hot docking/undocking the PCI bus or to add such functionality to an existing PCI device. While it is known to provide a DS bridge
623
in the side of the docking station or the PCI-PCI bridge with a function of an initiator to generate a dummy bus cycle, this means that a special function is added to these bridges and will restrict selection of bridges.
“Thinkpad 76X, 77X”, IBM notebook computer, (Thinkpad is a trademark of International Business Machines Corporation) provides a PCI-PCI bridge within the computer for hot docking/undocking the PCI bus line of the docking station to and from the PCI bus line of the computer.
FIG. 19
shows a schematic block diagram showing this technology. In this technology, when a computer
631
is disconnected from a docking station
633
and operates alone, a PCI-PCI bridge
635
is in a disabled state and is not recognized by other devices on PCI bus
637
. When the computer
631
is mounted to the docking station
633
while the computer is in operations the PCI bus line
637
is not affected by its bus cycle because the PCI-PCI bridge
635
disconnects the PCI bus line
637
from the PCI bus line
639
. The docking station then invokes software to interrupt the computer and the BIOS which receives it enables the PCI-PCI bridge
635
. However, because a signal, which is unique to devices and different from a signal which is common to the devices, exists in the signals of the PCI bus in this technology, the number of bus lines connected to the PCI-PCI bridge has to be increased in correspondence to the number of PCI devices on the docking station. Accordingly the number of bus lines passing a connector
641
increases if the PCI-PCI bridge is provided in the computer side and causes the expandability of the docking station to be impeded.
Further, PUPA8-6668 which was invented by the inventor of this patent application and assigned to the applicant of this patent application, discloses a technology in which a CPU monitors REFRESH# signal of the ISA bus to have the buses connected at the start time of a refresh cycle for hot docking/undocking. This technology takes advantage of an empiricism that the activity of the ISA bus is relatively low at the start time of the refresh cycle so that a signal waveform is not likely to be affected by coupling the buses.
Further, PUPA 5-73489 discloses a technology relating to hot docking/undocking of modules on a system bus to which a CPU and a plurality of modules are connected. In this technology, signals on the system bus are monitored by a bus cycle wait system in hot docking a device and the docked device does not receive data on the system bus when another device is transferring data on the system bus. Therefore, there is no likelihood that wrong data will be received and will incidentally match the receiving criteria of that device, putting the status of the end of receipt on a status bus. This technology grants a start permission to that device subject to a condition that data of other devices is not transferred on the system bus.
It is an object of this invention to provide an apparatus and a method of hot docking/undocking between a bus line, such as a PCI bus which interconnects devices of a computer system and peripheral devices of the computer, by adding a simple hardware to the computer.
It is another object of this invention to provide an apparatus and a method for monitoring a turn around cycle of a PCI bus line to hot dock/undock to and from a bus line at a time when noise will not affect a bus cycle when docked or undocked.
It is a further object of this invention to provide a connecting apparatus and method for hot docking/undocking in which there is no need to provide a device for acquiring the ownership of a bus for docking/undocking.
It is a further object of this invention to provide a connecting apparatus and method for hot docking/undocking in which there is no need to provide a PCI-PCI bridge in a computer for hot docking/undocking.
It is a further object of this invention to provide a connecting apparatus and method for hot docking/undocking which does not require a special function in a hot docked/undocked peripheral device.
SUMMARY OF THE INVENTION
The principle of this invention lies in f
Cameron Douglas W.
Dougherty Anne Vachon
Myers Paul R.
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