JPH04364627A - Communication bus changeover system - Google Patents

Abstract

PURPOSE:To realize the communication bus changeover system in which no-hit changeover of communication is attained in the case of inter-equipment communication by linking equipments in a loop. CONSTITUTION:Equipments (A)1, (B)2a and (C)2b having a MAC layer, an LLC layer and a host layer are connected in duplicate in a loop by using a 0 system communication bus 3 and a 1-system communication bus 4. For example, the equipment (A)1 is used for a bus management equipment and other non- management equipments, that is, the equipments (B)2a and (C)2b inform a bus fault to a host layer of its own equipment and inform an alarm to the equipment (A)1a. When the equipment (A)1a receives an alarm notice, the equipment (A)1a sends a transmission stop, bus changeover and transmission start command to the equipments (B)2a and (C)2b to change over the bus.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION The present invention is applied to a communication bus switching system when devices are connected in a loop to perform inter-device communication.

0002

2. Description of the Related Art Conventionally, when devices are connected in a loop to communicate between devices, most of the communication buses have a single configuration, and even if the communication bus has a duplex configuration, when a communication bus failure occurs,
There were no guards in place to ensure continuous communication.

0003

[Problems to be Solved by the Invention] The conventional communication bus switching method described above has the disadvantage that it cannot be applied to switching systems, etc. that require continuous communication without momentary interruption even if the communication bus becomes impaired. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to provide a communication bus switching system capable of switching communication without momentary interruption by eliminating the above-mentioned drawbacks.

[0005]

Means for Solving the Problems The present invention provides communication bus switching in a communication system in which a plurality of devices having the configurations of a media access controller layer, a logical link controller layer, and an upper layer are connected to a communication bus in a loop. In this method, the communication bus has a duplex configuration, and any one of the plurality of devices acts as a bus management device, and upon receiving an alarm notification from another device in the event of a bus failure, the communication bus is configured to control the logical link controller layer. bus management means including bus switching instruction sending means for sending a communication bus switching instruction after instructing all other devices to stop transmission; and transmission start instruction sending means for sending a transmission start instruction after confirming the switching. , the other device includes a failure notification means for notifying a bus failure from its logical link controller layer to an upper layer when communication becomes impossible, and an alarm notification means for notifying an alarm to the bus management device. The present invention is characterized by comprising a bus switching means including:

[0006]

[Operation] The communication bus has a duplex configuration, and the bus management device manages this bus switching. That is, when a device other than the bus management device becomes unable to communicate, it notifies its upper layer of the bus failure and also notifies the bus management device of an alarm. When the bus management device receives this alarm notification, the logical link controller layer sends an instruction to stop transmission and switch the bus to all devices connected to the bus, and after confirming the switching, sends an instruction to start sending, and switches the bus. I do.

[0007] Therefore, even if the communication bus becomes impaired, communication information will not be lost, and it is possible to switch the bus without any communication interruption.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of a communication system according to an embodiment of the present invention, FIG. 2 is a block diagram showing the main parts of its bus management device, and FIG. 3 is a block diagram showing the main parts of its bus management device. FIG. 2 is a block configuration diagram showing main parts of a non-management device other than the above.

The communication system of this embodiment includes a media access controller layer (hereinafter referred to as MAC layer) and a logical link controller layer (hereinafter referred to as LLC).
It's called a layer. ), and a device (A) 1, a device (B) 2a, and a device (C) 2b having upper layer configurations.
In a communication bus switching method in a communication system in which the 0-system communication bus 3 is connected in a loop shape to the 0-system communication bus 3 as a communication bus, the present invention is characterized in that the 0-system communication bus 3
The device (A) 1 is equipped with a 1-system communication bus 4 which is provided in a redundant manner, and the device (A) 1 acts as a bus management device and, in the event of a bus failure, connects the device (B) 2a or device (C) 2, which is another non-management device.
a bus switching instruction sending means 11 for sending a communication bus switching instruction from the LLC layer to the device (B) 2a and the device (C) 2b after instructing the device (B) 2a and device (C) 2b to stop transmission; Device (B) 2a and device (C) 2b, which are non-managed devices, are equipped with a bus management means including a transmission start instruction sending means 12 that sends a transmission start instruction after confirmation of switching, and have become unable to communicate. In some cases, the bus switching means includes a failure notification means 21 for notifying a bus failure from the LLC layer to an upper layer, and an alarm notification means 22 for notifying an alarm to the device (A) 1.

Next, the operation of this embodiment will be explained with reference to the bus switching sequence diagram shown in FIG. In FIG. 4, device (A) 1 is a bus management device, and device (B) 2a and device (C) 2b are non-management devices, and for convenience of drawing, device (B) 2a and device (C)
2b are shown together.

[0012] In the device (B) 2a, the LLC layer sends transmission information from the upper layer (software) to the ACT (active) MAC layer. If the transmission process is not completed, the LLC layer notifies the upper layer of the bus failure and also notifies the SBY (replacement) MAC layer of an alarm. The SBY-based MAC layer is the device (
A) Send alarm information to the 1 MAC layer. The SBY-based MAC layer of device (A) 1 sends the received alarm information to the LLC layer, and the LLC layer notifies the upper layer of the alarm. Upon receiving the alarm notification, the upper layer of device (A) 1 sends M to the LLC layer.
Sends AC layer ACT/SBY (switching) instruction information. LLC layer is ACT/SBY from upper layer.
Upon receiving the instruction information, devices (B) 2a and (C)
2b is sent to the SBY system MAC layer. The SBY-based MAC layer is
)2a and (C)2b, a transmission stop instruction signal is sent onto the bus.

S of devices (B) 2a and (C) 2b
The BY system MAC layer receives the transmission stop instruction signal,
In addition to notifying the LLC layer, the MA of device (A) 1
A reception OK (ACK) signal is sent to the C layer.

L of devices (B) 2a and (C) 2b
When the LC layer receives the transmission stop instruction signal, the LC layer performs the ACT
A transmission stop signal is sent to the /SBY system MAC layer, and when the ACT/SBY system MAC layer receives the transmission stop signal, it stops the transmission operation.

The SBY-based MAC layer of the device (A) 1 sends reception OK signals from the devices (B) 2a and (C) 2b to the LLC layer.

[0016] The LLC layer of device (A) 1 is connected to device (B).
)2b and (C)2b, it issues a token deletion instruction to the ACT/SBY MAC layer of its own device. ACT/SBY type MAC
The layer stops generating tokens upon receiving the token deletion instruction signal.

Next, the LLC layer of device (A) 1 is S
A new ACT instruction signal for the MAC layer of devices (B) 2a and (C) 2b is sent to the BY-based MAC layer, and the SBY-based MAC layer sends the signal onto the bus.

S of devices (B) 2a and (C) 2b
When the BY system MAC layer receives the new ACT instruction signal, it notifies the LLC layer, and also
Sends a reception OK (ACK) signal to the AC layer.

L of devices (B) 2a and (C) 2b
When the LC layer receives a new ACT instruction signal from the MAC layer, it sends a new ACT instruction and a new S to the MAC layer.
Give BY instruction. The old SBY-based MAC layer of device (A) 1 sends reception OK signals from devices (B) 2a and (C) 2b to the LLC layer.

The LLC layer of the device (A) 1 is the LLC layer of the device (A) 1.
)2a and (C)2b receive OK signal (AC
K), the new AC is sent to the MAC layer of the own device.
T/new SBY instruction, and then sends a token erasure cancellation instruction to the new ACT-based MAC layer. New ACT type M
The AC layer generates a token upon receiving the token erasure cancellation instruction signal. Device (A) 1 checks whether the token has been restored, and after confirming the restoration, device (B) 2a
and (C) send the transmission start instruction signal to 2b to the new AC.
The signal is sent to the T-system MAC layer, and the MAC layer sends the transmission start instruction signal onto the bus. The new ACT system MAC layer of devices (B) 2a and (C) 2b receives the transmission start instruction signal, notifies the LLC layer, and also notifies the MAC layer of device (A) 1 that reception is OK (AC
K) send back a signal.

L of devices (B) 2a and (C) 2b
When the LC layer receives the transmission start instruction signal, it notifies the upper layer that communication is possible, and also transmits the new ACT type M
Sends a transmission stop cancellation instruction to the AC layer. The LLC layer of device (A) 1 includes devices (B) 2a and (
C) Upon receiving the reception OK (ACK) signal from 2b, it sends back a response to the MAC layer's ACT/SBY instruction to the upper layer.

[0022] The LLC layer of the device (B) 2a sends transmission information when transmission is not possible to the device (A) 1, and the device (A)
If a reception OK (ACK) signal is received from one MAC layer, the upper layer is notified of the completion of transmission.

[0023]

[Effects of the Invention] As explained above, according to the present invention,
Even if a communication bus fails, communication buses can be switched without losing communication information, and a communication bus switching method that can be applied to switching systems, etc. that requires continuous communication without momentary interruption has been obtained, and its effects are significant. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of a communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the main parts of the device (A) as the bus management device.

FIG. 3 is a block diagram showing the main parts of devices (B) and (C) as non-managed devices.

FIG. 4 is a bus switching sequence diagram showing the operation.

[Explanation of symbols]

1 Device (A) 2a Device (B) 2b Device (C) 30 series communication bus 41 series communication bus 11 Bus switching instruction sending means 12 Transmission start instruction sending means 21 Trouble notification means 22 Alarm notification means

Claims (1)

[Claims] 1. In a communication bus switching method in a communication system in which a plurality of devices having a configuration of a media access controller layer, a logical link controller layer, and an upper layer are connected to a communication bus in a loop, the communication bus is It has a redundant configuration, and when any one of the plurality of devices acts as a bus management device and receives an alarm notification from another device in the event of a bus failure, it sends a notification from its logical link controller layer to all other devices. Bus management means includes bus switching instruction sending means for sending a communication bus switching instruction after a transmission stop instruction, and transmission start instruction sending means for sending a transmission start instruction after switching is confirmed, and other devices are configured to The bus switching means includes a failure notification means for notifying a bus failure from the logical link controller layer to an upper layer when the logical link controller layer falls into an impossible state, and an alarm notification means for notifying an alarm to the bus management device. A communication bus switching system characterized by: