JP2002278852A - Method and device for bus switching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly switch a serial bus to be used for accessing a serial device appropriately according to a situation. SOLUTION: A host 101 accesses the serial bus device 111 through an SMBus 104 normally. A microcomputer 103 detects whether the SMBus 104 is usable, in the case of detecting the SMBus 104 to be not usable, the microcomputer 103 operates FET switches 108 and 109 to perform switch control to cut off the device 111 from the SMBus 104 and to connect the device 111 to a local I2CBus. In the case of receiving the instruction of communication to the device 111 from a host 101 through an interface 102, the microcomputer 103 communicates with the device 111. When communication is completed, the microcomputer 103 informs the host the effect through the interface 102.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bus switching method and a bus switching apparatus, and more particularly to a bus switching method and a bus switching apparatus applied to a system that can access a serial bus device via a serial bus.

[0002]

2. Description of the Related Art Some computer systems include a CPU that controls the operation of the entire system, and a chip set including various bridges and the like that provide an interface between buses. This chipset is sometimes called a host.

[0003] The host operates the SM during system operation.
A serial bus device connected to a serial bus such as a bus is accessed as needed, and communication is performed with the serial bus device.

Since the serial bus in this case is used not only by the host but also by various devices,
When the usage rate of the SM bus increases, it may become difficult for the host to access the serial bus device.

[0005]

For example, if the use rate of the SM bus increases while the host is communicating with the serial bus device, the serial bus device to be communicated times out and the communication is interrupted. Could be

Further, when a temporary or fixed failure occurs in the serial bus, the host cannot communicate with the serial bus device because the serial bus cannot be used until the recovery processing is completed. There is a problem that can not be performed.

[0007] In view of the above, it is desirable to be able to perform communication by another serial bus without any trouble when one serial bus cannot be used.

The present invention has been made in view of the above situation, and provides a bus switching method and a bus switching apparatus capable of appropriately switching a serial bus used for accessing a serial bus device according to a situation. The purpose is to:

[0009]

A bus switching device according to the present invention comprises a first device which can access a serial bus device via a first serial bus, and a second device which is connected to a second serial bus. A bus switching device applied to a system comprising: a first switching unit configured to connect / disconnect between the serial bus device and the first serial bus; Second switching means for connecting / disconnecting with the second serial bus, and operating the first and second switching means so that the first device And the serial bus device can be accessed via the second serial bus.

Further, the bus switching device according to the present invention provides
A host accessible to the serial bus devices via the M bus, a bus changeover device applied to a system that includes a micro computer connected to the I 2 ^C bus, and the SM bus and the serial bus device A first switch for connecting / disconnecting between the serial bus device and a ^second switch for connecting / disconnecting between the serial bus device and the I ² C bus; and the first and second switches. By operating the host, the host can access the serial bus device via the microcomputer and the I ² C bus.

Further, a bus switching method according to the present invention includes a first device that can access a serial bus device via a first serial bus, and a second device connected to the second serial bus. A bus switching method applied to a system comprising: detecting whether or not the first serial bus can be used, and detecting that the first serial bus cannot be used. In this case, switching control for disconnecting the serial bus device from the first serial bus and connecting the serial bus device to the second serial device is performed, and access from the first device to the serial device is controlled by the second serial device. It can be performed via an apparatus and the second serial device.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the appearance of an information processing system to which a bus switching device according to the first and second embodiments of the present invention is applied.

The information processing system 1 has a configuration in which a plurality of information processing units are housed in a cabinet rack. The plurality of information processing units include, for example, units (main housings) 10 and 20 functioning as servers, and additional units (extended housings) 11 and 12 having hard disks mounted thereon.
1, an extension unit (expansion housing) equipped with a DAT 12,
22 and the like. In this example, a configuration in which functions are duplicated to maintain redundancy is employed.

FIG. 2 is a perspective view showing an overview of the units 10 and 20 constituting the information processing system. The unit 10 and the unit 20 are arranged side by side and housed in one housing. Unit 11 and unit 21, unit 12 and unit 22
Has the same configuration.

The bus switching devices according to the first and second embodiments are provided in the units 10 and 20, respectively. Since the units 10 and 20 have the same configuration, the bus switching device provided in the unit 10 will be described below.

First, a first embodiment of the present invention will be described. FIG. 3 is a block diagram showing a configuration including the bus switching device according to the first embodiment of the present invention.

The host 101 corresponds to, for example, a chip set including various bridges for performing an interface between buses and the like.
11 is accessed as needed, and communication with the serial bus device 111 is performed.

At normal times, the host 101
Access to the serial bus device 111 is performed by using the bus 104. On the other hand, in an emergency when the SM bus 104 cannot be used, the microcomputer 103 instructs the microcomputer 103 to communicate with the serial bus device 111 via the host interface (I / F) 102.

The host interface 102 is a host 1
01 and the microcomputer 103.

The microcomputer 103 communicates with the host 101 via the host interface 102,
Communication with various devices connected to the local I ² C bus 106 is performed. Further, the microcomputer 103 responds to an instruction from the host 101 to operate the serial bus device 11.
1 communicates with the host 1
01 is notified.

The SM bus 104 is a serial interface connected to the host 101. A serial bus device 111 can be connected to the SM bus 104 via a switch 105.

The switch 105 is provided between the serial bus device 111 and the SM bus 104, and performs connection / disconnection according to attachment / detachment of a jumper wire.

The local I ² C bus 106 is connected to the microcomputer 1
The serial bus is connected to the unit 03 and can communicate with other units (housings) other than the unit 10. Also, a serial bus device 111 can be connected to the local I ² C bus 106 via a switch 107.

The switch 107 is provided between the serial bus device 111 and the local I ² C bus 106,
Connect / disconnect according to the installation / removal of jumper wires.

[0026] Note that the SM bus 104 and the local ^{I 2} C bus 106, although the protocol is different, since they match with respect to the physical layer, can be connected to each other.

In the above configuration, in the initial setting, a jumper wire is attached to the switch 105 and the switch 107 is connected.
To remove the jumper wire. As a result, the host 101 normally communicates with the SM bus 10
4 can access the serial bus device 111.

On the other hand, when the usage rate of the SM bus 104 becomes high and it becomes clear that the host 101 cannot access the serial bus device 111 within the prescribed time limit, for example, when the SM bus 104 cannot be used. Then, the jumper wire is removed from the switch 105, and the jumper wire is attached to the switch 107. This allows
The host 101 can access the serial bus device 111 via the microcomputer 103 and the local I ² C bus 106.

When the SM bus 104 returns to a usable state, the jumper wire is removed from the switch 107 and the jumper wire is attached to the switch 105. As a result, the host 101 communicates with the SM bus 104 as usual.
To the serial bus device 111 via the.

As described above, according to the first embodiment, S
By attaching / detaching the jumper wires to / from the switches 105 and 107 according to the state of the M bus 104, the host 101 can access the serial bus device 111 via the appropriate serial bus without any trouble.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing a configuration including a bus switching device according to the second embodiment of the present invention. Elements common to those in FIG. 3 are denoted by the same reference numerals, and a specific description thereof will be omitted. Hereinafter, the points different from the first embodiment will be mainly described.

In the second embodiment, the switch 105 and the switch 107 using jumper wires are not used.
And 109 are used. These FET switches 108 and 109 respectively control the control signal 10 from the microcomputer 103.
They are turned on / off by 8a and 109a.

The microcomputer 103 includes an SM bus 10
A detection circuit for detecting the state of No. 4 is provided.
The microcomputer 103 dynamically switches and controls the FET switches 108 and 109 based on the detection result of the detection circuit.

When the microcomputer 103 detects that the SM bus 104 can be used, the microcomputer 103 switches the FET switch 10
8 is connected, and the FET switch 109 is turned off. On the other hand, when detecting that the SM bus 104 cannot be used, the FET switch 108 is turned off and the FET switch 109 is turned on. For example,
The microcomputer 103 controls the SM bus 104 in the following cases.
Is considered to be in an unusable state.

When the SM bus 104 hangs due to a temporary failure. The usage rate of the SM bus 104 exceeds a predetermined value.
When the serial bus device 111 is about to run out. When a fixed failure occurs in the SM bus 104. When the host 101 is stopped and the serial bus device 111 needs to operate in another operation mode. Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, the detection circuit of the microcomputer 103 determines whether or not the SM bus 104 is in an unusable state (step A1). If it is detected that the SM bus 104 cannot be used, the microcomputer 103 operates the FET switches 108 and 109 to switch the serial bus device 111 to be connected to the local I ² C bus 106. Control (step A
2).

The microcomputer 103 determines whether there is communication from the host 101 (step A3). If there is no communication from the host 101, communication from the microcomputer 103 to the serial bus device 111 is performed (step A4), and the process ends.

On the other hand, in the case of communication from the host 101,
The host 101 issues a communication instruction to the microcomputer 103 via the host interface 102 (step A).
5). As a result, the microcomputer 103 sets the local I ² C
Communication with the serial bus device 111 is performed via the bus 106 (step A6). When the communication is completed, the microcomputer 103 notifies the host 101 via the host interface 102 (step A7), and the process ends.

If it is detected in step A1 that the SM bus 104 can be used,
The microcomputer 103 operates the FET switches 108 and 109, and the serial bus device 111
(Step A8).
Thus, the host 101 performs communication with the serial bus device 111 via the SM bus 104.

As described above, according to the second embodiment, the serial bus used for accessing the serial bus device can be dynamically switched according to the state of the SM bus 104. In addition, installation of jumper wire /
It is not necessary to perform the removal, and it is possible to automatically select and control an appropriate serial bus.

The present invention is not limited to the above-described embodiment, but can be implemented with various modifications within the scope of the invention. For example, in the above embodiment, the SM bus and the I ² C bus are handled as the serial bus.
It is also possible to apply another thing such as 32C.

[0041]

As described above, according to the present invention, the serial bus used for accessing the serial bus device can be appropriately switched according to the situation.

[Brief description of the drawings]

FIG. 1 is an exemplary view showing an appearance of an information processing system to which a bus switching device according to first and second embodiments of the present invention is applied.

FIG. 2 is a perspective view showing an overview of units constituting the information processing system.

FIG. 3 is a block diagram showing a configuration including a bus switching device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration including a bus switching device according to a second embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the second embodiment.

[Explanation of symbols]

1 ... information processing system 10～12,20～22 ... Unit 101 ... Host 102 ... host interface 103 ... microcomputer 104 ... SM Bus 105 ... Switch 106 ... local ^{I 2} C bus 107 ... Switch 108 ... FET switch 109 ... FET switch

Claims (10)

[Claims] 1. A bus switching system applied to a system including a first device accessible to a serial bus device via a first serial bus and a second device connected to a second serial bus. An apparatus, comprising: first switching means for connecting / disconnecting between the serial bus device and the first serial bus; and connecting / disconnecting between the serial bus device and the second serial bus. And second switching means for performing
By operating the first and second switching means, the first device can access the serial bus device via the second device and the second serial bus. Bus switching device. 2. The bus switching device according to claim 1, wherein said first and second switching means perform said connection / disconnection according to attachment / detachment of a jumper wire. Means for detecting whether or not the first device can use the first serial bus; and means for not allowing the first device to use the first serial bus. 2. The control device according to claim 1, further comprising: a switching control unit configured to switch the first switching unit to a disconnection state and to switch the second switching unit to a connection state when an event is detected. Bus switching device. 4. The bus switching device according to claim 1, wherein said detection means and said switching control means are mounted on said second device. 5. A bus switching device applied to a system comprising a host accessible to a serial bus device via an SM bus and a microcomputer connected to an I ² C bus, wherein the serial bus device A first switch for connecting / disconnecting between the I / C bus and the SM bus; and a second switch for connecting / disconnecting between the serial bus device and the I ² C bus. And a second switch that allows the host to access the serial bus device via the microcomputer and the I ² C bus. 6. The bus switching device according to claim 5, wherein said first and second switches perform said connection / disconnection according to attachment / detachment of a jumper wire. 7. A circuit for detecting whether or not the host is ready to use the SM bus, and a circuit for detecting the first state when the host is detected to be unable to use the SM bus. 6. The bus switching device according to claim 5, further comprising switching control means for switching so that a switch is turned off and said second switch is turned on. 8. The bus switching device according to claim 7, wherein said detection circuit and said switching control means are mounted on said second device. 9. A bus switch applied to a system including a first device accessible to a serial bus device via a first serial bus and a second device connected to a second serial bus. A method for detecting whether the first serial bus is in a usable state, and, when detecting that the first serial bus is in an unusable state, changing the serial bus device to the first serial bus. Switching control for disconnecting from the first serial bus and connecting to the second serial device is performed, and access from the first device to the serial device is performed via the second device and the second serial device. A bus switching method characterized in that it can be carried out by using a bus. 10. The state detection and the switching control,
10. The method according to claim 9, wherein the step is performed by the second device.
The bus switching method described.