JPH11196099A - Method and system for data communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and system for data communication, where transfer of data is restarted by allowing someone to receive a message and finding out a fault to reconnect a disconnected cable, even when a person executing transfer of data is absent. SOLUTION: When the connection of a cable between a transfer source and a transfer destination is disconnected during data transfer, the transfer source and the transfer destination are separated into separate topology (step S302) and it is not found out that continuation of a print is impossible, a message denoting 'data transfer between such and such nodes is not normally finished because the topology is changed.' is informed of nodes connecting to the transfer source and the transfer destination at data transfer (step S303) to raise attention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of connecting a plurality of electronic devices (hereinafter, referred to as devices) by using a data communication bus capable of communicating control signals and data in a mixed manner. The present invention relates to a communication method and apparatus for performing data communication between devices.

[0002]

2. Description of the Related Art Conventionally, IEEE 1394-1995 Hi
gh Performance Serial Bus
In a plurality of devices connected via a 1394 serial bus (hereinafter, referred to as a 1394 serial bus), if any cable is disconnected (or remains disconnected) during printing (data transfer), If a bus reset occurs and the topology is reconfigured, but the source and destination have separated (or remain separate), the source will have the same topology as the destination. Until resetting, printing (transfer) cannot be resumed.

[0003]

In such a case, in the related art, if the person who executed the printing (transfer) was near the device, he or she noticed an abnormality, and connected the cable to print (transfer).
Can be resumed, but if the person is not aware of the abnormality because he or she is not near the device, there is a problem that the user is left in a printing (transfer) error state.

[0004] The present invention has been made in view of the above-mentioned problems of the above-described conventional technology, and an object of the present invention is to prevent a person who has executed data transfer from being close to the device. Another object of the present invention is to provide a data communication method and apparatus capable of resuming data transfer by reconnecting a disconnected cable by someone who notices an abnormality in response to the message.

[0005]

According to a first aspect of the present invention, there is provided a data communication method, wherein data transfer from a data transfer source to a transfer destination is normally completed in a device connected by a data communication bus. If the topology is separated into different networks due to disconnection of the cable before data transfer and data transfer cannot be continued, devices connected to the data transfer source / destination at the time of data transfer or node IDs before and after the data transfer ), An address detecting step of detecting an address of the device having, and a storing step of storing the address detected by the address detecting step.
A message transmitting step of transmitting a message to notify the node of the address of the abnormality to call attention.

[0006] In order to achieve the above object, a second aspect is provided.
The data communication method according to claim 1, wherein the data communication bus is a 1394 serial bus.

[0007] In order to achieve the above object, a third aspect is provided.
In the data communication device described above, the topology of the device connected to the data communication bus is separated into separate networks due to disconnection of the cable before the data transfer from the data transfer source to the transfer destination ends normally before the data transfer. If the transfer cannot be continued, the address of the device connected to the transfer source / destination of the data at the time of data transfer ("had a parent-child relationship") or the device having the preceding and following node IDs (identifiers) is detected. An address detecting means, a storing means for storing the address detected by the address detecting means, and a message transmitting means for transmitting a message for notifying the node of the address of the abnormality to call attention.

[0008] Further, in order to achieve the above object, the present invention relates to claim 4.
According to a third aspect of the present invention, in the data communication apparatus according to the third aspect, the data communication bus is a 1394 serial bus.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a data processing system to which a data communication apparatus according to an embodiment of the present invention is applied. In FIG. 1, reference numeral 101 denotes a digital video camera (DVCR); A personal computer (PC), 105 and 106 are printers, and 107 is a hard disk (HD). A digital video camera 101 and a personal computer 103 are connected to the personal computer 102 via a 1394 serial bus. The printer 105 includes personal computers 103 and 104 and a printer 106.
Connected via a serial bus. The personal computer 104 has 13 hard disks 107.
It is connected via a 94 serial bus.

In FIG. 1, a digital video camera 1 is shown.
01 is a node A, a personal computer 102 is a node B, a personal computer 103 is a node C, a printer 105 is a node D, and a personal computer 104.
Is a node E, the printer 106 is a node F, and the hard disk 107 is a node G. Also, in FIG. 1, node B (personal computer 102) to node D
(The printer 105).

FIG. 2 shows that during the data transfer shown in FIG. 1 (before the printing is normally completed), the node B (personal computer 102) as the transfer source and the node D (printer 105) as the transfer destination for some reason. ) Is disconnected due to disconnection of the cable, etc., and after a bus reset, the transfer source node B (personal computer 102) and the transfer destination node D (printer 105) have different topologies. This indicates a state in which data separation (printing) cannot be continued due to separation. The node B (personal computer 102) and the node D (printer 105) store the addresses of the nodes connected to each other (in a parent-child relationship), and after the bus reset occurs and the topology changes, the nodes B (personal computer 102) and node D (printer 105) If these nodes exist in the node B, the cable is disconnected from those nodes, and the transfer source node B (personal computer 1
02) transmits a message indicating that data transfer to the transfer destination node D (printer 105) has not been completed normally.

Next, the operation of the data communication apparatus according to one embodiment of the present invention will be described with reference to FIG. FIG. 3 is a flowchart showing an operation procedure of the data communication device according to one embodiment of the present invention.

In FIG. 3, when data transfer is started, first, in step S301, it is determined whether or not a bus reset has occurred due to some reason such as disconnection of a cable connecting a transfer source and a transfer destination during data transfer. to decide. If the bus reset does not occur, the process proceeds to step S307, and the data transfer ends normally. If a bus reset has occurred, the process proceeds to step S302 to determine whether the transfer source and the transfer destination are included in the same topology. If the transfer source and the transfer destination are included in the same topology, the process returns to step S301 to restart the data transfer. If the transfer source and the transfer destination are not included in the same topology, and the data transfer cannot be resumed, the process proceeds to step S303 and the transfer source and the transfer are performed before the bus reset (before the topology is changed). The addresses of the nodes connected to the destination (in a parent-child relationship) are detected and stored, and in those nodes, the node B which is the transfer source because the topology has changed (the cable has been disconnected)
The personal computer 102 transmits a message that the data transfer to the transfer destination node D (printer 105) is not completed normally to warn the user. Further, the transmission destination of the message is not a parent-child relationship, but may be a node having a node ID before and after the transfer source and the transfer destination.

Next, it is determined whether or not the cable disconnected in step S304 is reconnected until the cable is reconnected. If the disconnected cable is reconnected, the node B (personal computer 10
2) It is determined whether or not the node D (the printer 105) is included in the same topology. If the transfer source and the transfer destination are included in the same topology, the process returns to step S301 to restart the data transfer, and normally ends the data transfer (printing). Further, when the transfer source and the transfer destination are not included in the same topology and the data transfer cannot be resumed, a data transfer error occurs in step S306 due to the timeout time set for each node.

Next, in the present embodiment, a digital I / F (interface) for connecting each device is
Since an IEEE 1394 serial bus is used, this I
The EEE1394 serial bus will be described.

A consumer digital VTR (Video Ta)
With the advent of pe Recorders: video tape recorders and DVD (Digital Video Disk) players, it is necessary to support real-time and high-information data transfer of video data, audio data, and the like. .
Such video data and audio data are transferred in real time and sent to a personal computer (Personal Computer: P
In order to capture the data in C) or transfer the data to another digital device, an interface capable of high-speed data transfer having a necessary transfer function is required. An interface developed from such a viewpoint is IEEE1394. -1995 High Perform
An ance Serial Bus (hereinafter, referred to as a 1394 serial bus).

FIG. 4 is a block diagram showing the configuration of a network system configured using a 1394 serial bus. This system is a device (digital device)
A, B, C, D, E, F, G, H
-Between B, between devices A and C, between devices BD, between devices DE,
1394 serial bus twisted pair cable 4 between devices C and F, between devices C and G, and between devices C and H
01. These devices A to H are:
For example, a personal computer, a digital VTR (Video Tape)
Recorder: Video tape recorder), DV
Examples include a D player, a digital camera, a hard disk, and a monitor.

The connection method between the devices is such that the daisy chain method and the node branch method can be mixed.
A highly flexible connection is possible.

Each of the devices A to H has its own unique ID (identifier).
One network is configured in a range connected by a 94 serial bus. Just connect each device sequentially with one 1394 serial bus cable.
Each device plays a role of relay, and constitutes one network as a whole. In addition, it has a function of automatically recognizing the device and recognizing the connection status and the like when a cable is connected to the device by the 1394 serial bus and the Plug & Play function.

In the system shown in FIG. 4, when a device is deleted from the network or newly added, the bus reset is automatically performed, and the network configuration up to that time is reset. From
Rebuild a new network. With this function, the configuration of the network at that time can be constantly set and recognized.

The data transfer rate is 100/200.
/ 400 Mbps, and a device having a higher data transfer rate supports a lower data transfer rate to achieve compatibility.

In the data transfer mode, A for transferring asynchronous data such as a control signal (hereinafter, referred to as Async data) is used.
Synchronous transfer mode and synchronous data such as real-time video data and audio data (Iso
There is an Isochronous transfer mode for transferring (chronous data: hereinafter referred to as Iso data). The Async data and the Iso data include a cycle start packet (CS) indicating a cycle start in each cycle (usually, 125 μs per cycle).
After the transfer of P), the transfer of the Iso data is transferred in a mixed cycle within the cycle, while the transfer of the Iso data is prioritized over the Async data.

FIG. 5 shows the components of the 1394 serial bus.

The 1394 serial bus has a layer (hierarchical) structure as a whole. In FIG. 5, 50
Reference numeral 1 denotes a 1394 connector port to which a 1394 serial bus cable 502 is connected. The cable and connector of the 1394 serial bus are connected. 139
On the four connector port 501, hardware (h
The physical layer 503 and the link layer 504 are positioned as (ardware) sections. The hardware section is a substantial interface chip section. Among them, the physical layer 503 performs encoding and material-related control, and the link layer 504 performs packet transfer and cycle time control. Transaction layer 5 of firmware section
05 manages data to be transferred (transacted) and issues Read, Write, Lock commands. The serial bus management layer 506 of the firmware section manages the connection status and ID of each connected device and manages the network configuration.

The hardware section and the firmware section constitute a substantial 1394 serial bus.

The application layer 507 of the software section differs depending on the software to be used, and is a section for specifying how data is loaded on the interface, and defines a printer, an AVC protocol, and the like.

The above is the configuration of the 1394 serial bus.

FIG. 6 is a diagram showing an address map in the 1394 serial bus.

Each device (node) connected to the 1394 serial bus must have a 64-bit address unique to each node. By storing this address in a ROM (read only memory), the node address of the user or the other party can always be recognized, and communication in which the other party is specified can be performed.

The addressing of the 1394 serial bus is based on the IEEE 1212 standard. In FIG. 6, the first 10 bits are used for specifying the bus number and the next 6 bits are used for specifying the node ID number. You. The remaining 8 bits become the address width given to the device, and can be used as a unique address space. The last 28 bits store information such as identification of each device and designation of use conditions as an area of unique data.

The above is the outline of the technology of the 1394 serial bus.

Next, the technical portion which can be said to be a feature of the 1394 serial bus will be described in more detail.

First, the electrical specifications of the 1394 serial bus cable will be described.

FIG. 7 is a sectional view of a 1394 serial bus cable. In the figure, reference numeral 701 denotes a 1394 serial bus cable, which has 6 pins, that is, two sets of twisted pair signal lines 702 and a power supply line 703. As a result, power can be supplied to a device having no power supply, a device whose voltage has dropped due to a failure, and the like. The voltage of the power supply flowing through the power supply line 703 is 8 to 40 V,
The current is specified at a maximum current of DC 1.5 A. Each set of twisted pair signal lines 702 is covered with a signal line shield 704.

In a standard called a DV cable, the power supply line 703 is formed by four pins without the power supply line 703.

Next, the DS-Link (Data / Str)
(Link) coding will be described.

FIG. 8 is a diagram for explaining the DS-Link encoding method of the data transfer format adopted in the 1394 serial bus.

In the 1394 serial bus, DS-Lin
A k-coding scheme is employed. This DS-Link coding method is suitable for high-speed serial data communication.
The configuration requires two signal lines. The main data (Data) is sent to one of the twisted pair wires, and the strobe (Strobe) signal is sent to the other twisted pair wire. The receiving side reproduces a clock by taking an exclusive OR of the communicated data and the strobe.

Advantages of using such a DS-Link coding method include higher transfer efficiency as compared with 8 / 10B conversion, and PLL (Phase-Lock Loop).
p: a phase lock loop (LCL) circuit is not required, so that the controller LSI (Large Scale Integra
Since the circuit scale of an attached circuit (large-scale integrated circuit) can be reduced, and there is no need to send information indicating an idle state when there is no data to be transferred, the transceiver circuit of each device is set to a sleep state. By doing so, power consumption can be reduced.

Next, the sequence of the bus reset will be described.

In the 1394 serial bus, each connected device (node) is given a node ID and recognized as a network configuration. When there is a change in the network configuration, for example, when a change occurs due to an increase or decrease in the number of nodes due to insertion / removal of a node or power-on (ON) / off (OFF), and a new network configuration needs to be recognized. , Each node that has detected a change transmits a bus reset signal on the bus to enter a mode for recognizing a new network configuration.

At this time, a change is detected by detecting a change in the advice voltage on the 1394 port board.

When a bus reset signal is transmitted from a certain node, the physical layer 503 (see FIG. 5) of each node receives the bus reset signal and, at the same time, generates a bus reset in the link layer 504 (see FIG. 5). And a bus reset signal to other nodes.
After all the nodes finally detect the bus reset signal, the bus reset is activated.

The bus reset can also be performed by starting by hardware detection due to cable insertion / removal or network abnormality as described above, and directly issuing a command to the physical layer 503 (see FIG. 5) by host control from a protocol or the like. to start.

When the bus reset is activated, the data transfer is suspended, and the data transfer during this time is suspended.
When finished, it will be restarted under the new network configuration.

The above is the bus reset sequence.

Next, a sequence for determining a node ID will be described.

After the bus reset, each node enters an operation of giving each node an ID in order to construct a new network configuration. At this time, from the bus reset to the node I
A general sequence between the D determinations will be described with reference to the flowcharts of FIGS. 9, 10, and 11.

First, from the occurrence of the bus reset, the node ID
Will be described with reference to FIG. 9 until the data transfer can be performed.

First, it is determined in step S901 whether a bus reset has occurred in the network or not. When a bus reset occurs due to power on / off or the like, the process proceeds to the next step S902. This step S
At 902, from a state where the network is reset,
In order to know the connection status of the new network, a parent-child relationship is declared between the directly connected nodes.

Next, in step S903, it is determined whether or not the parent-child relationship has been determined between all the nodes. If determined, one route is determined in the next step S904. Also,
If the parent-child relationship is not determined between all the nodes, the process returns to step S902 to declare the parent-child relationship again, and the route is not determined.

When one route is determined in step S904, in the next step S905, each node
A node ID setting operation for giving D is performed. Then, a node ID setting operation is performed in a predetermined node order, and it is determined in the next step S906 whether IDs have been set for all nodes. If the ID setting has not been completed, the process returns to step S905, and a node ID setting operation for giving an ID to each node again is performed. If the ID setting has been completed in step S906, data transfer between nodes is performed in the next step S907, and the process returns to step S901 to determine whether a bus reset has occurred in the network again. Judge until it occurs.

Next, the operation of determining the parent-child relationship in the bus reset will be described with reference to FIG.

First, it is determined in step S1001 whether or not a bus reset has occurred in the network, and if so, the flow advances to the next step S1002. In step S1002, a flag (FL) indicating that each device is a leaf (node) is used as the first stage of re-recognizing the reset network connection status.
Stand up. Next, in step S1003, it is checked how many ports of each device are connected to other nodes. Next, in step S1004, step S10
In accordance with the confirmation result of the number of ports in 03, in order to start the declaration of the parent-child relationship from now on, it is determined how many ports are undefined (the parent-child relationship is not determined).

Here, immediately after the bus reset, the number of ports =
Although the number of undefined ports is determined, the number of undefined ports detected in step S1004 changes as the parent-child relationship is determined.

First, immediately after the bus reset, the declaration of the parent-child relationship can be initially made only to the leaves. A leaf can be known by checking the number of ports in step S1003. Leaf step S
After declaring "I am a child and my partner is a parent" for the notebook connected to myself in 1007, this processing operation is terminated.

Further, since the number of ports is more than one in step S1003 and the number of unrecognized ports is more than 1 in step S1004 immediately after the bus reset, the node recognized as a branch is executed in step S1008.
In step S1009, a flag “FL” is set in the parent-child relationship declaration from the leaf.
arent) ". Then, the leaf declares the parent-child relationship, and the step S1009 is described.
The branch that has received it in step S
Returning to step 904, the number of undefined ports is confirmed. If the number of undefined ports is 1, the node connected to the remaining port is referred to in step S1007 as "I am a child and the other is a parent. "Can be declared. For the second and subsequent times, even if the number of undefined ports is checked in step S1004, for a branch having two or more ports, in step S1009, a "parent" from a leaf or another branch is accepted again. wait.

Finally, if any one branch or exceptional leaf (because it did not operate quickly because a child declaration can be made) becomes 0 as a result of checking the number of undefined ports in step S1004, As a result, the declaration of the parent-child relationship of the entire network has been completed, and the only node for which the number of undefined ports has become 0 (all are determined as parent ports) is set with a root flag (FL) in step S1005. . Next, step S
After the route is recognized in 1006, this processing operation ends.

Thus, the operation from the bus reset shown in FIG. 10 to the declaration of the parent-child relationship between all the nodes in the network is completed.

Next, the operation between the determination of the parent-child relationship in the bus reset and the determination of the node ID will be described with reference to FIG.

In the above-described sequence up to FIG. 9 and FIG. 10, flag information of each node such as leaf, branch, and route is set. , Determine what the flag is. As a task of assigning an ID to each node, it is possible to first set an ID from the leaf. The IDs are set in ascending order of leaf → branch → route (node number = 0).

If the flag is leaf in step S1101, the process proceeds to step S1102, if the flag is a route, the process proceeds to step S1114, and if the flag is a branch, the process proceeds to step S1108.

Step S1 to proceed when the flag is leaf
At 102, the number N of leaves existing in the network
(N is a natural number) is set. Next, in step S1103, each leaf requests the root to give an ID. If there are multiple requests, the route is
Arbitration is performed in 1114, and step S11
An ID number is given to one node that has won the arbitration in 15 and a failure result is notified to the node that has lost the arbitration. Next, in step S1104, it is determined whether or not the ID has been obtained. If the leaf has failed in obtaining the ID, the process returns to step S1103, where an ID request is made again, and the same operation is repeated.

Also, in step S1104, I
In the case of a leaf for which D has been obtained, in step S1105, the ID information of the node is transferred to all nodes by broadcasting (a function of notifying the determined own node ID to all other nodes). When the broadcast of the one-node ID information ends, the number N of the remaining leaves is reduced by one in the next step S1106. Next, step S
In 1107, it is determined whether or not the number N of the remaining leaves is zero. And when the number N of the remaining leaves is 1 or more,
Returning to step S1103, the operation is repeatedly performed from the ID request operation, and finally, when all the leaves broadcast the ID information, the number N of the remaining leaves becomes 0, so the flow proceeds to the next step S1108.

In step S1108, the number M (M is a natural number) of branches existing in the network is set. Next, in step S1109, each branch requests to give an ID to the root. On the other hand, in the route, arbitration (arbitration) is performed in step S1116, and branches are given in order from the branch that has won the arbitration, starting from the next youngest number that has been given to the leaf. Next, in step S1117, the route notifies the branch that issued the request of ID information or a failure result. Next, in step S1110, it is determined whether or not the ID has been acquired.
In the case of a leaf for which acquisition of D has failed, the flow returns to step S1109, where an ID request is made again, and the same operation is repeated.

In step S1110, I
In the case of the branch from which D could be obtained, step S1111
Transmits the ID information of the node to all nodes by broadcasting. When the broadcast of the one-node ID information ends, the number N of remaining leaves is reduced by one in the next step S1112. Next, step S1113
It is determined whether or not the number N of the remaining branches is zero.
If the number N of the remaining branches is 1 or more, the process returns to the step S1109 to repeat the operation from the ID request, and finally, when all the branches broadcast the ID information, the number N of the remaining branches is reduced. Since it becomes 0, the process proceeds to step S1118.

In this step S1118, when the process ends so far, the root node is the only node that does not finally use the ID information as a seed. Therefore, the lowest number that has not been given is set as its own ID number, and the next step S1119 is performed.
After the broadcast of the route ID information, the present processing operation is terminated.

In step S1101, if the flag indicates a branch, the processing after step S1108 is performed, and if the flag is a root, the processing after step S1114 is performed.

As described above, the procedure from the determination of the parent-child relationship to the setting of the IDs of all the nodes is completed as shown in FIG.

Next, the operation in an actual network will be described as an example with reference to FIG.

In FIG. 12, a node A and a node C are directly connected below the (root) node B, a node D is directly connected below the node C, and a node D is further connected below the node D. Has a hierarchical structure in which nodes E and F are directly connected.

In FIG. 12, a branch is a node having two or more node connections, a leaf is a node having only one port connection, port c is a port corresponding to a child node, and port p is a parent node. The corresponding port.

A procedure for determining the hierarchical structure, the root node, and the node ID will be described below.

After the bus reset, the node A first declares the parent-child relationship. Basically one of the nodes
A node with a connection to only one port (called a leaf) can declare a parent-child relationship. Since the user can first know that only one port connection is established, it recognizes that this is the end of the network, and the parent-child relationship is determined from the node that has operated earlier in the network. Thus, the port on the side that has declared the parent-child relationship (node A between nodes AB) is set as a child,
The port on the other end (node B) is set as the parent. Thus, a child-parent is determined between nodes AB, a child-parent is determined between nodes ED, and a child-parent is determined between nodes FD.

Further, one level higher, a node having a plurality of connection ports (referred to as a branch) is sequentially assigned a parent-child relationship declaration to a higher order from a node that has received a parent relationship declaration from another node. I will go. In FIG. 12, first, after the parent-child relationship between the node D and the node D-F is determined, the node D declares a parent-child relationship with the node C. As a result, the child-parent and the node I have decided.

The node C that has received the declaration of the parent-child relationship from the node D becomes the node B connected to another port.
Declare a parent-child relationship. by this,
The child-parent is determined between the nodes C and D.

In this way, a hierarchical structure as shown in FIG. 12 is formed, and the parent node B in all finally connected ports is determined as the root node.

There is only one route in one network configuration.

In FIG. 12, the node B is determined to be the root node. This is because the node B, which has received the parent-child relationship declaration from the node A, declares the parent-child relationship to other nodes at an early timing. If so, the root node may have moved to another node. That is, depending on the transmission timing, any node may become the root node, and the root node is not always constant even in the same network configuration.

When the root node is determined in this way, the process enters a mode for determining each node ID. Here, all nodes notify their determined node IDs to all other nodes (broadcast function).

The self ID information includes its own node number, information on the connected position, the number of ports it has, the number of connected ports, information on the parent-child relationship of each port, and the like.

The procedure for assigning node ID numbers is as follows:
First, it can be started from a node (leaf) that has connection to only one port, and node number =
.. Are assigned as 0, 1, 2,.

The node that has acquired the node ID broadcasts information including the node number to each node. Thereby, it is recognized that the ID number is “assigned”.

When all the leaves have acquired their own node IDs, the process moves to the branch, and the node ID numbers following the leaves are assigned to the respective nodes. Similarly to the leaf, the node ID information is broadcast sequentially from the branch to which the node ID number is assigned, and finally, the root node broadcasts its own ID information. That is, the root always owns the largest node number.

As described above, the assignment of the node IDs of the entire renovation structure is completed, the network configuration is reconstructed, and the bus initialization operation is completed.

Next, arbitration will be described with reference to FIG.

In the 1394 serial bus, the arbitration (arbitration) of the right to use the bus must be performed before data transfer.
I do. Since the 1394 serial bus is a logical bus type network in which each device connected individually relays the transferred signal to transmit the same signal to all devices in the network, packet collision occurs. Arbitration is necessary to prevent
This allows only one node to transfer at a given time.

FIGS. 13A and 13B are diagrams for explaining the arbitration process. FIG. 13A shows a state in which a request for a bus use right is delivered, and FIG. 13B shows a state in which a bus use permission is delivered. Are respectively shown.

When arbitration starts, one or more nodes issue a bus use request to the parent node. Nodes C and F in FIG. 13A are nodes that have issued a bus use right request. The parent node (node A in FIG. 13A) that has received this further issues (relays) a request for the right to use the bus toward the parent node. This request is finally delivered to the arbitration route.

The root node that has received the request for the right to use the bus determines which node uses the bus. This arbitration work can be performed only by the root node, and the node that has won the arbitration is given permission to use the bus. FIG.
3 (b), use permission is given to the node C, and the node F
Indicates a state of being denied.

A DP (Data Prefix) packet is sent to the node that has lost arbitration,
Notify rejection. The request for the right to use the bus of the rejected node is kept waiting until the next arbitration.

As described above, the node that has won the arbitration and has been granted the use of the bus can start transferring data thereafter.

Here, a flow of a series of arbitration operations will be described with reference to the flowchart of FIG.

In order for a node to be able to start data transfer, the bus must be idle. In order to recognize that the data transfer previously performed is completed and the bus is currently idle, a predetermined idle time gap length (for example, a subaction gap) set individually in each transfer mode is required. ), Each node determines that its own transfer can be started.

In FIG. 14, first, at step S140
Asynchronous data at 1, Is
It is determined whether or not a predetermined gap length corresponding to data to be transferred, such as ochronous (synchronous) data, has been obtained.

Unless a predetermined gap length is obtained, a request for the right to use the bus necessary to start transfer cannot be made, so that the process waits until a predetermined gap length is obtained. If a predetermined gap length is obtained in step S1401, it is determined in step S1402 whether there is data to be transferred. If there is no data to be transferred, no processing is performed. When this processing operation ends and there is data to be transferred, the process proceeds to the next step S1403.

In step S1403, a request for the right to use the bus is issued to the root so as to secure a bus for transferring data. At this time, the transmission of the signal indicating the request for the right to use the bus is finally delivered to the route while relaying each device in the network, as shown in FIG.

Next, in step S1404, the above-described step S1404 is executed.
At least one route receives the request for the right to use the bus at 1403, and the route has the number of nodes requesting the right to use the bus at 1 or more (the number of nodes requesting the right to use the bus> 1) at the next step S1405. It is determined whether or not there is. And
If the number of nodes is one or more (the number of nodes requesting the right to use the bus> 1), the root determines arbitration (arbitration) in step S1406 to determine one node to which use permission is given.
Do the work. This arbitration work is fair, and only the same node is used every time.
It is structured to give equal rights (fair arbitration).

Next, in step S1407, the aforementioned step S
A selection operation of dividing one node (a node that has won the arbitration) whose route has been arbitrated and the use of which has been granted from the plurality of nodes that have issued the usage right request in 1406 into another node that has lost the arbitration is performed. Do. In this case, for one node that has been arbitrated and whose use has been permitted, or for a node that has been permitted to use without arbitration in step S1405 and the number of bus use request nodes = 1, the route is determined in step S1408 with respect to that node. After transmitting the permission signal, the processing operation ends. The node that has received the permission signal in step S1408 is
Immediately after reception, transfer of data (packet) to be transferred starts. Further, to the node that has lost the arbitration in step S1406 and has not been permitted to use the bus, a DP (Data Prefix) packet indicating an arbitration failure is sent from the root in step S1409, and the node that has received the packet transmits the arbitration again. In order to issue a request for a bus use right to perform
Then, the process waits until a predetermined gap length is obtained.

Next, Asynchronous (asynchronous) transfer will be described with reference to FIGS. Asynchronous transfer is asynchronous transfer.

FIG. 15 is a diagram showing a temporal transition state in the asynchronous transfer, and FIG. 16 is a diagram showing an example of a packet format of the asynchronous transfer.

In FIG. 15, the first sub-action
The gap (subaction gap) indicates an idle state of the bus. When the idle time reaches a certain value, the node desiring transfer determines that the bus can be used and executes arbitration for acquiring the bus.

When the bus use permission is obtained by arbitration, the data transfer is executed in the form of a packet.
After the data transfer, the receiving node sets ack (reception confirmation return code) of the reception result for the transferred data to a.
After a short gap of ck gap, the transfer is completed by returning and responding or sending a response packet. The ack includes 4-bit information and a 4-bit checksum, and includes information such as success, busy status, and pending status, and is immediately returned to the transmission source node.

A packet for synchronous transfer has a header in addition to a data part and data CRC for error correction. The header part has a destination node ID, a source node ID, The transfer data length, various codes, and the like are written and the transfer is performed.

Asynchronous transfer is one-to-one communication from a self-node to a partner node. The packet transferred from the transfer source node is distributed to each node in the network, but the address other than the address for itself is ignored, so that only one destination node reads the packet.

The above is the description of the asynchronous transfer.

Next, Isochronous (isochronous: synchronous) transfer will be described with reference to FIGS. Isochronous transfer is synchronous transfer.
Isochronous transfer, which can be said to be the greatest feature of the 1394 serial bus, is a transfer mode suitable for transferring data that requires real-time transfer, such as multimedia data such as video data and audio data.

In contrast to the one-to-one transfer in the asynchronous transfer, the isochronous transfer is uniformly transferred from one transfer source node to all other nodes by the broadcast function.

FIG. 17 is a diagram showing a temporal transition state in the isochronous transfer, and FIG. 18 is a diagram showing an example of a packet format of the isochronous transfer.

The isochronous transfer is executed on the bus at regular intervals. This time interval is called an isochronous cycle. The isochronous cycle time is 125 μs. The cycle start packet indicates the start time of each cycle, and plays a role of adjusting the time of each node. A node called a cycle master transmits a cycle start packet, and after a transfer in a previous cycle is completed, a predetermined idle period (subaction gap) is passed, and then the start of this cycle is announced. Send a cycle start packet.

The time interval transmitted to the cycle start packet is 125 μs.

FIG. 17 shows channels A, B,
As indicated by the channel C, a plurality of types of packets can be distinguished and transferred by giving a channel ID in one cycle. This allows real-time transfer between multiple nodes at the same time,
The receiving node takes in only the data of the channel ID desired by itself. The channel ID does not represent the address of the transmission destination, but merely gives a logical number for the data. Therefore, the transmission of a certain packet is transferred by broadcast from one source node to all other nodes.

Prior to the packet transmission in the isochronous transfer, arbitration is performed as in the asynchronous transfer. However, since the communication is not one-to-one communication as in the asynchronous transfer, there is no ack (reception confirmation reply code) in the isochronous transfer.

The iso gap (isochronous gap) shown in FIG. 17 indicates an idle period necessary for recognizing that the bus is empty before performing the isochronous transfer. After the predetermined idle period has elapsed, a node that wishes to perform isochronous transfer determines that the bus is free, and can perform arbitration before transfer.

Each isochronous transfer packet divided into each channel has a header portion in addition to a data portion and an error correction data CRC, and the header portion has a transfer data length and a length as shown in FIG. A channel number, other codes, an error correction header CRC, and the like are written and transferred.

The above is the description of the isochronous transfer.

Next, a bus cycle will be described with reference to FIG. FIG. 19 is a diagram showing a temporal transition state of a transfer state on a bus in which isochronous transfer and asynchronous transfer are mixed.

The isochronous transfer is executed prior to the asynchronous transfer. The reason is that, after the cycle start packet, the isochronous transfer can be orbited with a gap length (isochronous gap) shorter than the gap length (subaction gap) of the idle period required to start the asynchronous transfer.
Therefore, the isochronous transfer is executed with priority over the asynchronous transfer.

In the general bus cycle shown in FIG. 19, a cycle start packet is transferred from the cycle master to each node at the start of cycle #m. Thus, each node adjusts the time, and after a predetermined idle period (isochronous gap), the node that should perform isochronous transfer performs arbitration and starts packet transfer. In FIG. 19, the channel e, the channel s, and the channel k are sequentially isochronously transferred.

After the operations from the arbitration to the packet transfer are repeatedly performed for the given channel, when all the isochronous transfers in the cycle #m are completed, the asynchronous transfer can be performed.

When the idle time reaches the subaction gap where asynchronous transfer is possible, the node that wishes to perform asynchronous transfer determines that it can proceed to arbitration.

However, the period during which the asynchronous transfer can be performed is the time (cycle syn) for transferring the next cycle start packet after the end of the isochronous transfer.
This is limited to the case where a sub-action gap for activating the asynchronous transfer is obtained before the channel ch).

In cycle #m of FIG. 19, two packets (packet 1 and packet 2) of the isochronous transfer for three channels and the asynchronous transfer (including ack) are transferred thereafter. This asynchronous packet 2
After that, the time to start cycle m + 1 (cyc
le sync), the transfer in cycle #m ends here.

However, the time (cy) to transmit the next cycle start packet during asynchronous or synchronous transfer operation
If cle sync) is reached, a cycle start packet of the next cycle is transmitted without waiting for an idle period after the end of the transfer without forcibly interrupting the transfer. That is, when one cycle lasts for 125 μs or more, the next cycle is correspondingly shorter than the reference 125 μs. Like a child, the isochronous cycle can be exceeded or shortened on the basis of 125 μs.

However, the isochronous transfer is executed whenever necessary in order to maintain the real-time transfer, and the asynchronous transfer may be transferred to the next and subsequent cycles due to the shortened cycle time.

The cycle information including such delay information is
Controlled by the master.

[0128]

As described in detail above, according to the data communication method and apparatus of the present invention, during the data transfer from the source node to the destination node, the data transfer cannot be continued due to disconnection of the cable or the like. Even if the person who executed the data transfer did not notice that it fell into a state, the cable was disconnected from the node connected to the transfer source / transfer destination and the node with the previous and next node ID and the topology changed Since it is possible to notify that there is a node that has not successfully completed data transfer, even if the person who executed data transfer is absent, someone who noticed the message and noticed something wrong reconnected the disconnected cable As a result, there is an effect that data transfer can be resumed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a data processing system to which a data communication device according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a data processing system to which the data communication device according to the first embodiment of the present invention is applied.

FIG. 3 is a flowchart showing an operation flow of the data communication device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a data processing system using an IEEE 1394 cable.

FIG. 5 is a diagram showing a hierarchical structure of IEEE1394.

FIG. 6 is a diagram showing an address map of IEEE1394.

FIG. 7 is a sectional view of an IEEE 1394 cable.

FIG. 8 is a diagram for explaining a DS-Link encoding format.

FIG. 9 is a flowchart showing an operation flow from a bus reset to setting of an ID.

FIG. 10 is a flowchart illustrating a flow of an operation of determining a parent-child relationship in a bus reset.

FIG. 11 is a flowchart showing a flow of operation from determination of a parent-child relationship in a bus reset to determination of a node ID.

FIG. 12 illustrates a parent-child relationship between nodes.

FIG. 13 is a diagram for explaining a process of arbitration.

FIG. 14 is a flowchart showing a flow of an arbitration operation.

FIG. 15 is a diagram showing sub-actions in asynchronous transfer.

FIG. 16 is a diagram showing a packet structure in asynchronous transfer.

FIG. 17 is a diagram showing a sub-action in isochronous transfer.

FIG. 18 is a diagram illustrating a packet structure in isochronous transfer.

FIG. 19 is a diagram illustrating an example of a communication cycle of IEEE1394.

[Explanation of symbols]

 101 digital video camera (DVCR) 102 personal computer (PC) 103 personal computer (PC) 104 personal computer (PC) 105 printer 106 printer 107 hard disk (HD)

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Claims (4)

[Claims] 1. In a device connected by a data communication bus, before data transfer from a data transfer source to a transfer destination ends normally, a cable is disconnected and the topology is separated into different networks, and data transfer is stopped. If it cannot be continued, the devices connected to the source and destination of the data at the time of data transfer or the node IDs (identifiers) before and after
An address detecting step of detecting an address of a device having an address, a storing step of storing the address detected by the address detecting step, and a message transmitting step of transmitting a message that informs the node at the address of an abnormality to call attention. A data communication method comprising: 2. The data communication method according to claim 1, wherein said data communication bus is a 1394 serial bus. 3. In a device connected by a data communication bus, before data transfer from a data transfer source to a transfer destination is normally completed, a cable is disconnected and the topology is separated into different networks, and data transfer is stopped. If the data cannot be continued, address detection for detecting the address of the device connected to the source and destination of the data at the time of data transfer ("being in a parent-child relationship") or the device having the preceding and following node IDs (identifiers) A data communication device comprising: a unit; a storage unit configured to store an address detected by the address detection unit; and a message transmission unit configured to transmit a message for notifying an abnormality to a node at the address and calling attention. 4. The data communication device according to claim 3, wherein said data communication bus is a 1394 serial bus.