JP2004048535A - Ieee1394 communication unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IEEE communication unit in which the topology and the physical_ID of a bus fixed once definitely can be prevented from varying in the way of communication by preventing occurrence of a bus reset due to insertion of an extra cable. <P>SOLUTION: The communication unit performing communication through an IEEE1394 serial bus comprises a means for detecting connection of a cable 106 with a port, and switches 110 and 112 for connecting or disconnecting the port, and an operating section for turning the switches on/off. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a communication device that performs communication via an IEEE 1394 serial bus.
[0002]
[Prior art]
When the IEEE 1394 serial bus is used, various connection forms such as a daisy chain, a star, and a tree can be used for connecting the nodes. Therefore, in order to perform communication, it is necessary to identify the topology of the bus and determine the ID for specifying the node. According to the IEEE 1394 standard, a bus reset is generated when a cable is inserted or removed, and tree identification, self identification, and the like are automatically performed. At this time, the physical_ID of each node is dynamically assigned, and thereafter, each node is specified by the physical_ID.
When controlling a device connected via the bus, if the user wants to use a logical ID determined by the user to specify the device, the physical_ID is dynamically assigned after the bus reset. A process for knowing the correspondence of physical_ID is required. Further, if a bus reset occurs continuously due to an abnormal connection state such as a loop connection or a device failure, the tree state and physical_ID are not determined, and communication cannot be started forever.
There are several solutions to the problem of physical_ID, which changes when a bus reset occurs, and the problem of continuous bus resets. For example, the invention disclosed in Japanese Unexamined Patent Application Publication No. 2000-358040 is to detect a continuous bus reset so that a faulty device or a loop connection can be eliminated. And communication with a dynamically allocated identification code such as physical_ID is stored so that communication can be continued even after a bus reset, and the invention disclosed in Japanese Patent Application Laid-Open No. 2001-077839. Has a switch for opening and closing a port, and opens the switch by a loop event to release the loop connection.
[0003]
[Problems to be solved by the invention]
However, in the related art, the physical_ID of each node on the network is dynamically assigned after the occurrence of the bus reset, and cannot be determined in advance. There is no guarantee that the parent-child relationship of the nodes after the bus reset will be the same as before, and it is not clear which one will become the root node. In other words, there is a problem that even if the same cable is wired in the same device, there is no guarantee that the same physical_ID is assigned before and after the bus reset.
In view of the above, the present invention considers that a connection is constituted only by a device assumed in advance, adopts a mechanism that does not allow additional connection of devices, prevents a bus reset due to additional cable insertion, and establishes a bus topology once determined. It is an object of the present invention to provide an IEEE communication device that can avoid that the physical_ID and physical_ID change during communication.
[0004]
[Means for Solving the Problems]
In order to solve the above problem, the present invention according to claim 1, in a communication device that performs communication via an IEEE 1394 serial bus, detecting means for detecting that a cable is connected to a port, and connecting or disconnecting the port. A switch for disconnecting, and a switch operating unit for opening and closing the switch, and after the physical_ID is determined by bus reset, the switch operating unit operates the switch to disconnect an unconnected port to connect an additional device. Is rejected.
According to a second aspect of the present invention, there is provided an IEEE 1394 communication device for performing communication via an IEEE 1394 serial bus, comprising: a detecting unit for detecting that a cable is connected to a port; and a switch for connecting or disconnecting the port. And a switch operation unit for opening and closing the switch. After the physical_ID is determined by a bus reset or the like, the switch operation unit operates a switch to disconnect an unconnected port, and a bus reset is performed by pulling a cable or the like. The switch operating unit operates the switch so that all ports are connected regardless of whether the cable is connected or not when the switch is connected.
Also, according to the present invention, after the physical_ID is determined by the bus reset, the switch operation unit operates the switch and disconnects the unconnected port after a predetermined time elapses. It is characterized by doing.
With this configuration, it is possible to prevent a bus reset from occurring due to additional cable insertion.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the IEEE 1394 communication apparatus of the present invention. The communication device A 101, the communication device B 102, the communication device C 103, the communication device D 104, and the communication device E 105 are an IEEE 1394 communication chip 107, input / output ports A and B 108 and 109, switches A and B 110 and 111, a connection detection & switch control unit 112, respectively. Is provided. A switch is provided for each port, and serves to connect or disconnect the IEEE 1394 cable 106 and the IEEE 1394 communication chip 107. The connection detection & switch control unit 112 detects connection of the IEEE1394 cable 106 and performs opening / closing operations of the switches A, B110 and 111. As the connection detecting means, for example, the communication device is provided with a connector for inserting the IEEE 1394 cable 106, and the connection is detected by attaching a photo interrupter so that the output changes when the connector of the IEEE 1394 cable 106 is inserted, or a limit switch is connected to the connector. It is conceivable to attach the cable and detect the cable insertion by pressing the limit switch when the cable is inserted into the connector.
It is also conceivable that the connection detection & switch control unit 112 of the present invention has a cable insertion / removal detection circuit based on a change in bias voltage provided in the conventional IEEE 1394 physical layer.
[0006]
First, the four nodes of the communication devices A to D 101 to 104 are connected by the IEEE 1394 cable 106, and the power is turned on. At first, it is assumed that all switches of the four communication devices A to D 101 to 104 are closed and the IEEE 1394 cable 106 is connected to the IEEE 1394 communication chip 107. When the communication devices are connected by a cable, a bus reset occurs, and after all self IDs have been received, the detection & switch control unit 112 of each communication device detects a port to which no cable is connected in its own node. Then, by opening the switch, the port to which the IEEE 1394 cable 106 is not connected is disconnected. In FIG. 1, switches of one port of the communication device A101 and one port of the communication device D104 to which nothing is connected are open, and are in a state of not accepting additional connection. That is, the group 113 is fixed to only four communication devices.
[0007]
Next, it is assumed that an additional connection of the communication device E105 to the fixed group 113 is attempted. The IEEE 1394 cable 106 connected to the communication device E105 is inserted into a vacant connector of the communication device D104. Since the switch of the port 2 of the communication device D104 into which the cable is additionally inserted is open, the IEEE 1394 cable 106 is not connected to the IEEE 1394 communication chip 107, and no bus reset occurs in the fixed group 113. Therefore, the physical_ID determined by the fixed group 113 does not change.
[0008]
Next, a description will be given of a second embodiment of the IEEE 1394 communication apparatus according to the present invention. In each of the communication devices, the time from when a bus reset occurs and physical_ID is determined to when an unconnected port is detected and a switch is opened is set in advance and stored. In the above-described first embodiment, after a bus reset occurs and all self IDs have been received, the detection & switch control unit of each communication device detects a port to which no cable is connected at its own node. The connection detection & switch control unit 112 of each communication device does not operate until the time from the detection of the unconnected port to the opening of the switch elapses. After a lapse of time from the detection of an unconnected port to the opening of a switch, each communication device detects the port to which a cable is not connected in its own node by the detection & switch control unit 112 and opens the switch. This disconnects the port to which the IEEE 1394 cable 106 is not connected.
Next, a third embodiment of the IEEE 1394 communication apparatus of the present invention will be described with reference to FIG. First, it is assumed that the IEEE 1394 cable 106 connected to the communication device E of the first embodiment is connected to the port 2 of the communication device D104 where the switch is open. At this time, only the fixed group 113 composed of four nodes configures the network, and the communication device E105 cannot communicate with another communication device. A procedure for joining the communication device E105 to a fixed group according to the present invention will be described. As shown in FIG. 3, in the state of FIG. 2, the communication device D105 side of the IEEE 1394 cable 106 connecting the communication device C103 and the communication device D104 is pulled out. At this time, since the connection state of the fixed group 113 has changed due to the removal of the IEEE 1394 cable 106, a bus reset occurs. Then, as shown in FIG. 4, the switches of all ports are closed by the occurrence of the bus reset. Thereafter, the cable that has been pulled out is re-inserted into the communication device D105 before the elapse of a preset time from the detection of an unconnected port to the opening of the switch, as shown in FIG. Then, since the connection is performed with the switches of all the communication devices closed, a bus reset occurs in a state where the communication devices A to E101 to 105 are connected. After the bus reset, when the time from when the unconnected port is detected to when the switch is opened elapses, the switch of the cable unconnected port is opened, and the state becomes as shown in FIG. That is, the group 601 is fixed to only the five communication devices A to E101 to 105.
However, in the state of FIG. 4, if the time from when the unconnected port is detected to when the switch is opened has elapsed, the switch of one port of the communication device D104 is opened as shown in FIG. The connection between C103 and the communication device D104 cannot be established. In this case, there are two unconnected networks of a fixed group A 701 including the communication devices A to C 101 to 103 and a fixed group B 702 including the communication device D 104 and the communication device E 105.
[0009]
Further, as a fourth embodiment of the present invention, it is not the lapse of time from the detection of a preset unconnected port to the opening of the switch described in the third embodiment as a condition for opening and closing the switch. Opening and closing the switch under conditions is conceivable. For example, the root node transmits data for disconnecting an unconnected port to all nodes, and each communication device opens a switch of a cable unconnected port when receiving data for disconnecting an unconnected port.
The case where each communication device has two ports has been described above, but the same mechanism can be used even when each communication device has three or more ports.
[0010]
【The invention's effect】
As described above, the IEEE 1394 communication device according to claim 1 includes a detection unit that detects that a cable is connected to a port, a switch that connects / disconnects the port, and a switch operation unit that opens and closes the switch. After the physical_ID is determined by a bus reset or the like, the switch operating unit operates the switch to disconnect the unconnected port and reject the connection of the additional device. Can be prevented from occurring, and there is an effect that a change in physical_ID once determined is not caused.
The IEEE 1394 communication device according to claim 2, further comprising: detection means for detecting that a cable is connected to the port, a switch for connecting / disconnecting the port, and a switch operation unit for opening and closing the switch. After the physical_ID is determined by a bus reset or the like, the switch operation unit disconnects an unconnected port by operating a switch, and when a bus reset occurs by pulling out a cable or the like, regardless of whether the cable is connected or disconnected. Since the switch operation unit operates the switch so as to connect all the ports, there is an effect that when an additional device is desired to be connected, the existing connection can be disconnected once and then connected.
In the IEEE 1394 communication device according to the third aspect, after a physical_ID is determined by a bus reset or the like, a predetermined time elapses, and then the switch operation unit operates a switch to disconnect an unconnected port. Therefore, when a bus reset occurs due to pulling out of a cable or the like, the switch operation unit operates the switch so that all ports are connected regardless of whether the cable is connected or not connected. Has the effect of allowing you to set a grace period before rejecting an additional device.If you want to connect an additional device, you must disconnect the existing connection and then connect it. It has the effect of being able to connect.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of an IEEE 1394 communication device according to the present invention; FIG. 2 is a diagram showing a state where a device is added; FIG. 3 is a diagram showing pulling out of a connected IEEE 1394 cable; FIG. FIG. 5 is a diagram showing a state in which switches of all ports are closed by FIG. 5 FIG. 5 is a diagram showing re-insertion of an IEEE 1394 cable within a set time from the state of FIG. 4 FIG. 6 is a diagram showing a state in which all devices are connected Diagram showing a state after a lapse of a set time from the state of FIG.
101 Communication device A
102 Communication device B
103 Communication device C
104 Communication device D
106 IEEE 1394 cable 107 IEEE 1394 communication chip 108 port A
109 Port B
110 Switch A
111 Switch B
112 Connection detection & switch control unit 113 Fixed group 601 Fixed group 701 Fixed group A
702 Fixed group B

Claims (3)

In an IEEE 1394 communication device that performs communication via an IEEE 1394 serial bus,
Detecting means for detecting that a cable is connected to the port;
A switch for connecting or disconnecting a port,
A switch operation unit that opens and closes the switch,
An IEEE 1394 communication device, wherein after a physical_ID is determined by a bus reset, the switch operating unit operates a switch to disconnect an unconnected port and reject connection of an additional device. In an IEEE 1394 communication device that performs communication via an IEEE 1394 serial bus,
Detecting means for detecting that a cable is connected to the port;
A switch for connecting or disconnecting a port,
A switch operation unit that opens and closes the switch,
After the physical_ID is determined by the bus reset, the switch operation unit disconnects the unconnected port by operating the switch, and when a bus reset occurs by pulling out the cable, regardless of whether the cable is connected or disconnected. An IEEE 1394 communication device, wherein the switch operation unit operates a switch so as to connect all ports. 3. The method according to claim 1, wherein after a physical_ID is determined by a bus reset, the switch operation unit operates a switch to disconnect an unconnected port after a predetermined time has elapsed. An IEEE 1394 communication device as described.

Images