JP2001230835A - Data communication system and data communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data communication system and a data communication method that can maintain high-speed performance of data communication. SOLUTION: Nodes 101, 103 each having a control circuit conducting transmission reception processing for a data signal include a plurality of bus lines that serially connect the nodes 102, 103 and the control circuit includes a delay time provision circuit that delays a re-transmission time from the reception of a busy acknowledge signal 71 until re-transmission of the same data signal from a transfer source node 101 to a transfer destination node 103 in the case of receiving the busy acknowledge signal 71 that is used by the transfer destination node 101 to inform the transfer source node 101 about the disabled reception of the data signal sent from the transfer source node 101 sending the data signal to the transfer destination node 103 receiving the data signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data communication apparatus and a data communication method for transmitting and receiving data signals between serially connected communication networks.

More specifically, the present invention relates to a data communication device and a data communication method that include an interface according to the IEEE 1394 standard or the like, and that transmit and receive signals between serially connected communication networks.

[0003]

2. Description of the Related Art Heretofore, personal computers and peripheral devices such as video cameras, digital still cameras, scanners, printers, mice, and keyboards have been connected using different connectors and cables.

According to such a method, a separate interface is often required for each peripheral device, and various cables are extended from a personal computer to complicate the connection.

[0005] As a standard for unifying the interface of peripheral devices, Skudgee (Small Computer S)
system (SCSI) standards exist. The interface of the scuzzy standard has a high speed, and is used for connection between a personal computer and a peripheral device requiring a high speed. Peripheral devices requiring high speed include, for example, an external hard disk storage device and a compact disk (CD) reading device.

[0006] The connection according to the scuzzy standard is a daisy-chain connection method. When the interface of the scuzzy standard is used, a plurality of peripheral devices, such as a digital still camera and a handy scanner, which are often used by connecting to the end of a communication network, cannot be connected to the same interface.

[0007] Therefore, there has been a demand for an interface which has a unified standard, is capable of high-speed transmission, and is capable of simple connection.

[0008]

Recently, unification for connecting peripheral devices, such as digital video cameras, handy scanners, and digital still cameras, which input / output data related to multimedia technology to information processing devices such as personal computers. Interface as
IEEE1394 standard or USB (Universal)
(Serial Bus) standard has been proposed and its practical use is progressing.

An interface based on the IEEE 1394 standard and an interface based on the USB standard are both interfaces used for serial connection.

These interfaces can serially connect a number of nodes (connection points existing between communication networks, specifically, personal computers and peripheral devices). Therefore, the connection relationship between the nodes is simplified. The number of connectable nodes is as large as 63, and the distance between the nodes can be increased.

[0011] A communication network using an interface based on the USB standard and the IEEE 1394 standard requires synchronization data (I) that must guarantee completion of information transfer.
Synchronous data transfer for transferring sochronous data and asynchronous data (Asynchronous) for guaranteeing that data is always transmitted to the destination node
data), which is two types of data transfer functions of asynchronous data transfer.

Incidentally, regarding the data communication speed, U
The maximum data transfer rate when using the interface based on the SB standard is, for example, 12 Mbit / s, whereas the data transfer rate when using the interface based on the IEEE 1394 standard is, for example, 100, 20.
It has three data transfer rates of 0 and 400 Mbit / s. When an interface based on the IEEE 1394 standard is used, higher-speed data transfer is possible as compared with a case where an interface based on the USB standard is used.

Using a plurality of digital video cameras,
When building a system to monitor at the same time, use USB
Rather than using a standard interface, the IEEE
It is more advantageous to use an interface according to the 1394 standard. The interface based on the USB standard is suitable for serial connection between a personal computer and peripheral devices such as a keyboard and a mouse, which do not require much high speed.

In the interface according to the USB standard,
The bus arbitration function is provided only to the host controller. In contrast, IEEE 1394
In the interface according to the standard, a bus arbitration function is provided to the controller LSIs of all nodes.

By having the above characteristics, the IEEE
A communication network using an interface based on the 1394 standard exhibits the following functions.

1) A broadcast function capable of simultaneously transmitting data to all nodes on a bus line (cabling between nodes).

2) A multicast function capable of simultaneously transmitting data to a plurality of nodes on a bus line.

3) A synchronization function that allows nodes on the bus line to operate simultaneously.

4) A bus snooping function capable of monitoring the status of a bus line.

Synchronous data transfer is used to transfer so-called multimedia data such as moving images and audio.

According to the IEEE 1394 standard, synchronous data transfer guarantees that data transfer is completed every 125 μs. This is to prevent images and sounds from "jerking".

On the other hand, asynchronous data transfer can be used for ordinary computer data transfer.

In the asynchronous data transfer, it is guaranteed that data is always transmitted to the partner node. It is not guaranteed until the data transfer is completed.

In the asynchronous data transfer, data is transferred by a memory mapped I / O method. That is, data is sent from one node to the address space of another node. Each node ignores communication data unless the address of its own node is specified.

By the way, the IEEE 1394 standard or US
In the case of performing data communication (transfer) in the asynchronous data transfer mode using a serially connected communication network using an interface based on the B standard or the like, in particular, IEEE 139
When data communication (transfer) in the asynchronous data transfer mode is performed using a serially connected communication network using an interface based on the 4 standards, a considerably high speed data communication should be possible as described above. Regardless, a phenomenon such as an unexpectedly delayed time until data arrives at the destination (transfer destination) node occurs.

An object of the present invention is to provide data communication, in particular, IEEE.
An object of the present invention is to provide a data communication technique capable of maintaining high-speed data communication when performing asynchronous data transfer using a serial connection communication network using an interface based on the E1394 standard or the like.

[0027]

According to one aspect of the present invention, there are provided a plurality of nodes each having a control circuit for transmitting and receiving data signals, and a plurality of communication cables for serially connecting the nodes. In the control circuit,
A busy acknowledgment signal for notifying the transfer source node that the data signal transmitted from the transfer source node transmitting the data signal to the transfer destination node receiving the data signal cannot be received by the transfer destination node is received. A data communication device including a delay time providing circuit for delaying a retransmission time from when the busy acknowledge signal is received to when the same data signal is retransmitted from the source node to the destination node. Is provided.

According to another aspect of the present invention, a plurality of nodes each including a control circuit for performing a transmission / reception process of a data signal, and a plurality of communication cables (bus lines) for serially connecting the nodes are provided. A) transmitting a data signal from a source node transmitting the data signal to a destination node receiving the data signal, and b) receiving the data signal using the data communication device. When the transfer source node receives a busy acknowledge signal notifying the transfer source node that the transfer was not possible,
Suspending retransmission of data from the source node during a predetermined pause period starting from receiving the busy acknowledgment signal; c) after the pause period, the source node returns to the destination node again. Retransmitting the data signal toward the data communication method.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following embodiments, I
Using an interface based on the EEE1394 standard,
A case where asynchronous data transfer is performed using a serially connected communication network will be described as an example. However, an asynchronous type data transfer is performed using a serially connected communication network using an interface based on another standard (eg, USB standard). The case where the data transfer is performed is also included.

There are various data communication systems. In the embodiment described below, a case where a packet communication method is mainly used will be described as an example.
However, other communication methods are also included.

When asynchronous data transfer is performed using a communication network using an interface based on the IEEE 1394 standard, the inventor theoretically and experimentally investigates the cause of congestion on a bus line as a data transfer path. Study was carried out.

Next, an asynchronous data transfer in a serial communication network using an interface based on the IEEE 1394 standard will be described.

FIG. 1 shows a configuration example of a communication network using an interface based on the IEEE 1394 standard. In this example, there are six nodes from node A to node F in the communication network.

There are two types of nodes, a node called a leaf and a node called a branch. A leaf is a node that is connected to only one device (for example, a personal computer). The branch is 2
A node connected to one or more devices. Devices that are not turned on are included in the device count.

In FIG. 1, nodes A, E and F are leaves. Nodes B, C, and D are branches. Each node has one or more ports. A bus line BL connecting the nodes is connected between the ports included in the nodes.

The first operation performed in automatically setting the communication network is the operation of resetting the bus line BL. When the reset operation starts, all the nodes stop reading and writing operations and stop data transfer.

Next, a phase for recognizing where the node is located in what kind of tree structure is entered.

By exchanging signals bidirectionally between the nodes, it is determined whether the own port is the parent port p or the child port c with respect to the port included in the partner node.

The port included in the previously queried node becomes a child. When the parent-child relationship is determined, the whole becomes a complete tree structure.

In FIG. 1, only Node B has no child ports. Node B is the parent to all nodes and is called the root. There is only one root in a serially connected tree-structured communication network.

The arbitration (ar) described above
When the tree structure of the communication network is determined by the (bitration) step, the node number of the communication network is then determined.
Move on to step D).

The step of determining the node number (self ID) will be described with reference to FIG.

After performing the above arbitration step, each node sends out its own ID packet.

The information included in the self-ID packet includes its own node number, where it is in the communication network, how many ports the node has, how many devices are connected to each port, and Whether each port is a parent or a child. The node that has first acquired arbitration, for example, node A in FIG.
To win.

The node A sends out a self ID packet having information of the node number (0). Since this packet is broadcast, all nodes know that “node number (0)” has been allocated.

Next, the node C that has acquired the arbitration becomes the node number (1). By transmitting the self ID packet having the information of the node number (1) by the node E,
Inform other nodes that “node number 1” has also been assigned.

Arbitration is performed so that the order in which all the nodes A to F send their own ID packets is the leaf first, the branch next, and the root last. The route always sends the self ID packet last. The root node B has the largest node number, for example, (5).

One communication network serially connected using an interface based on the IEEE 1394 standard can connect up to 63 nodes. The bus lines can be expanded up to a total of 1023 lines. That is, a maximum of 1023 × 63 devices can be connected.

When the step of deciding the self ID is completed, an idle state called an arbitration reset gap is entered. The initialization of the bus line is completed, and asynchronous transfer or synchronous transfer becomes possible.

The time from the reset of the bus line to the completion of the above initialization is about 200 μs. The time required for initialization varies depending on the number of nodes.

The step of requesting the right to use the bus based on FIG. 3 will be described.
The step of sending an “a.prefix” signal will be described.

A communication network serially connected using an interface based on the IEEE 1394 standard always performs arbitration of the right to use the bus prior to data transfer.

At a time, only one node performs data transfer. No data signal collision occurs.

As shown in FIG. 3, when arbitration starts, one or more nodes issue a request for the right to use the bus toward the parent node (indicated by arrows parallel to the bus lines). The parent node further requests the right to use the bus toward the parent node. This request is finally delivered to route B.

As shown in FIG. 4, the route B that has received the request for the right to use the bus line determines which node uses the bus line. A bus license is given to the node that has acquired the arbitration. At the same time, for nodes (nodes A and F) for which arbitration could not be acquired, DP (data prefix) is used.
x) Send a signal. Upon receiving the DP signal, the request for the right to use the bus line is rejected.

The node that has obtained the bus line license sends a signal indicating the transfer speed before starting data transfer. Usually three different data transfer rates (100 Mbit /
Second, 200 Mbit / sec, and 400 Mbit / sec).

In the asynchronous transfer method, data is sent from one node to the address space of another node.
The node ignores data signals applied to other than its own address.

The packet signal is transmitted from the communication transfer source node to the transfer destination node. When the transfer destination node returns an acknowledgment or returns a response packet, a transaction (a series of processing that occurs when transmitting and receiving desired data) is completed.

When the destination node receives the data of the asynchronous packet signal, the destination node must return an acknowledgment to all nodes.
The content of the acknowledgment is success or busy. However,
No arbitration is required to return the acknowledgment.

The transfer destination node needs to return a response packet as soon as possible.

When the transfer destination node is busy in the reception processing and cannot receive the packet, it informs that the packet cannot be received at present. To do so, a busy acknowledge signal is returned to the transfer source node. Upon receiving the busy acknowledge signal, the transfer source node transmits the packet signal again to the transfer destination node.

FIG. 5 shows a more specific traffic diagram relating to data (packet) communication using an asynchronous data transfer unit created by the inventor based on an experiment. Here, for simplicity, the operation will be described focusing on communication between two nodes (the transfer source node 1 and the transfer destination node 3).

At time t 1, first packet signal 5 is transmitted from source node 1 to destination node 3. The first packet signal 5 reaches the transfer destination node 3 at time t2. At time t3, an acknowledgment signal 11 indicating that the reception was successful is returned, and at time t4, the acknowledgment signal 11 is received by the transfer source node 1.

In the transfer destination node 3, the reception processing T1 of the first packet signal 5 starts at time t3.

At time t5, the second packet signal 15 is transmitted from the source node 1 to the destination node 3. The second packet signal 15 reaches the transfer destination node 3 at time t6.

However, the transfer destination node 3 cannot receive the second packet signal 15 because the reception processing T1 of the first packet signal 5 is performed.

At time t7, the transfer destination node 3 transmits a busy acknowledge signal 21 for notifying the transfer source node 1 that the second packet signal 15 cannot be received to the transfer source node 1. At time t8, the transfer source node 1 receives the busy acknowledge signal 21.

The transfer source node 1 having received the busy acknowledge signal 21 retransmits the second packet signal 15 at time t9. Retransmitted second packet signal 15
Arrives at the transfer destination node 3 at time t10. The transfer destination node 3 cannot receive the second packet signal 15 because it is performing the reception processing T1 of the first packet signal 1.

At time t11, the transfer destination node 3
The busy acknowledge signal 21 is transmitted to the transfer source node 1 again. The transfer source node 1 receives the busy acknowledge signal 21 at time t12.

The transfer source node 1 having received the busy acknowledge signal 21 retransmits the second packet signal 15 at time t13. Retransmitted second packet signal 15
Arrives at the transfer destination node 3 at time t14.

The transfer destination node 3 receives the first packet signal 5
, The second packet signal 15 cannot be received yet. At time t15, the transfer destination node 3 transmits the busy acknowledge signal 21 to the transfer source node 1. The transfer source node 1 receives the busy acknowledge signal 21 at time t16. The transfer source node 1 that has received the busy acknowledge signal 21 retransmits the second packet signal 15 at time t17. The retransmitted second packet signal 15 has a time t
At 18, the packet reaches the transfer destination node 3.

As shown in the figure, the reception processing T1 of the first packet signal ends at a time before time t18. The second packet signal 15 is received by the destination node 3.

At time t19, a second acknowledgment signal 31 indicating that the reception was successful is returned from the transfer destination node. At time t20, the transfer source node 1
Acknowledgment signal 31 is received.

In the transfer destination node 3, the reception processing T2 of the second packet signal 15 starts.

As described above, the retransmission packet signal and the busy acknowledgment signal are transmitted on the bus line connecting the source node 1 and the destination node 3 until the acknowledgment signal indicating the completion of reception is received from the destination node. And passes repeatedly.

The retransmission of the packet signal is performed immediately upon receiving the busy acknowledge signal. However, it is unlikely that the retransmitted packet signal will be ready for reception at the transfer destination node. This is because the transmission destination node is performing reception processing of the previously received packet signal and is likely to be busy. Therefore, the steps of transmitting the busy acknowledge signal and retransmitting the packet signal are repeated several times.

That is, when the acknowledgment signal is returned after transmitting the first packet signal, the reception processing of the first packet signal is performed at the transfer destination node.
Thereafter, if a busy acknowledge signal is returned when a new packet signal is sent, even if the packet signal is immediately retransmitted, the transfer of the retransmitted packet signal and the transfer of the busy acknowledge signal as described above. Is likely to be repeated. When such situations overlap, communication traffic on the IEEE serial bus increases.

The following conclusions were obtained. The first packet signal from the source node is received at the destination node, and an acknowledgment signal is returned to the source node. Thereafter, it is assumed that the transfer source node transmits a second packet signal, and the transfer destination node returns a busy acknowledge signal to the transfer source node. Immediately after that, even if the source node retransmits the same packet signal to the destination node,
The transfer destination node has a high probability of being busy.

Based on the above conclusion, a data communication device and a data communication method according to an embodiment of the present invention will be described below with reference to the drawings.

FIGS. 6 and 7 are functional block diagrams showing a control circuit included in the data communication apparatus.

The control circuit C shown in FIG.
Each node existing in a communication network serially connected using an interface based on the 4 standards, more specifically, for example, provided inside a controller LSI.

The control circuit C includes a busy acknowledge signal detection circuit 33, a delay time provision circuit 35, and a data signal retransmission circuit 37.

If the transfer destination node of the data signal (packet signal) is busy due to, for example, the reception processing of the packet signal transmitted before it and receives a new packet signal, the transfer destination node Returns a busy acknowledge signal to the transfer source node. A busy acknowledge signal 39 emitted from the transfer destination node is detected by the busy acknowledge signal detection circuit 33 of the transfer source node. The busy acknowledge signal detection circuit 33 outputs the busy acknowledge signal 39
Is detected, the busy acknowledgment reception signal 41 corresponding to the busy acknowledgment signal 39 is sent to the delay providing circuit 35 existing in the transfer source node.

The delay time providing circuit 35 of the transfer source node
When the busy acknowledgment reception signal 41 is received, the delayed busy acknowledgment reception signal (delayed busy acknowledgment reception signal) is sent to the data signal retransmission circuit 37 after a predetermined delay time tn has elapsed. This instructs the data signal retransmission circuit 37 existing in the transfer source node so that the transfer source node retransmits the same packet signal.

Data signal retransmission circuit 37 of transfer source node
Retransmits the packet signal 45 from the transfer source after an elapse of a predetermined delay time tn in response to an instruction from the delay time providing circuit 35.

A time sufficient for performing a reception process or the like is set as a delay time tn. After the delay time tn has elapsed,
The packet signal 45 retransmitted from the transfer source is received by the transfer destination node. An acknowledgment signal indicating successful reception is returned to the transfer source node.

It takes time for the receiving process of the transfer destination node,
In some cases, a busy acknowledge signal may be issued again from the transfer destination node. In this case, the delay time may be set again by the delay time giving circuit 35 for the same time, and then the busy acknowledge reception signal may be set. Alternatively, after the elapse of the delay time tn, the retransmission packet issued by the source node is
Further, when the busy acknowledge signal is issued, it is not necessary to wait so long, and therefore, it may be set so that a command to retransmit the packet signal is issued directly to the data signal retransmission circuit.

The delay time provided in the delay time providing circuit may be shortened. Alternatively, it may be set to 0 to immediately issue a command to retransmit the packet signal.

FIG. 7 shows a more detailed functional block diagram of the delay time providing circuit 35.

The delay time giving circuit 35 shown in FIG. 7 includes a delay time setting register 47, a counter 48, and a comparator 50. FIG. 8 is a timing chart showing the operation of the delay time providing circuit. The specific configuration and operation of the delay time providing circuit will be described with reference to FIGS.

FIG. 8A shows a busy acknowledge signal 51 input to the counter 48. FIG. 8B shows the output 52 of the counter 48. FIG. 8C shows the output 49 of the delay time setting register. FIG. 8D shows a busy acknowledge reception signal 53 obtained as an output of the comparator 50.

As shown in FIG. 8C, a delay time setting register 47 included in the delay time providing circuit 35 corresponds to a predetermined delay time, for example, tn, until the packet signal is retransmitted. Data "n" is stored.

The pulse-like busy acknowledge signal 51 shown in FIG. 8A is first input to the counter 48 shown in FIG. When the busy acknowledge signal is input, the counter 48 starts.

As shown in FIG. 8B, the counter 4
The output signal 52 of No. 8 sequentially increases with time from 0 to n. When the value of the output signal 52 of the counter 48 becomes equal to the output signal 49 (in this case, “n”) corresponding to the value of the predetermined delay time tn stored in the delay time setting register 47 in advance, FIG. As shown in d), the comparator 50 emits a pulse signal (detection signal) 53 delayed by the time tn. With this detection signal 53,
The packet signal 45 (FIG. 6) having the same contents as the above packet signal is retransmitted from the data signal retransmission circuit 37 (FIG. 6).

By changing the delay time tn stored in the delay time setting register 47, the time from the reception of the busy acknowledge signal to the retransmission of the packet signal can be arbitrarily set.

A communication network having the same configuration as the communication network to be implemented is constructed, and the actual communication status of the data signal is examined, for example, the state of data exchange and congestion. So that the delay time t
The value n corresponding to n may be stored in a register.

In an actual communication network, the congestion status may be monitored as appropriate, and the value corresponding to the delay time set in the register may be manually changed.

FIG. 9 shows a more specific traffic diagram when the above-described packet communication device is used. The operation will be described focusing on communication between two nodes (the transfer source node 101 and the transfer destination node 103).

At time t1, the first packet signal 55 is transmitted from the source node 101 to the destination node 103.
Is sent. The first packet signal 55 reaches the transfer destination node 103 at time t2. At time t3, an acknowledgment complete signal 61 indicating that the reception was successful
Is returned to the transfer source node 101.

At the transfer destination node 103, the reception processing T11 of the first packet signal 55 starts, for example, at time t3.

At time t4, an acknowledge complete signal 61 from the transfer destination node 103 reaches the transfer source node 101.

At time t5, the second packet signal 6 is transmitted from the source node 101 to the destination node 103.
5 is transmitted. The second packet signal 65 is at time t6
At the transfer destination node 103.

The transfer destination node 103 is in the process of receiving the first packet signal 55 and is in a state where it cannot receive the second packet signal 65 at present. At time t7, the transfer destination node 103 transmits the busy acknowledge signal 71 to the transfer source node 101. Source node 101
Receives the busy acknowledge signal 71 at time t8.

In the data communication device according to the present embodiment,
Transfer source node 10 receiving the busy acknowledge signal 71
1 does not immediately retransmit the packet signal. During a period from time t8 to time t9 (delay time tn = t9−t8), retransmission of the packet signal is not performed.

At time t9 when a predetermined delay time tn has elapsed, second packet signal 65 is retransmitted from transfer source node 101.

The above relationship can be expressed by the following equation: t9−t8
> T5-t4.

The retransmitted second packet signal 65 reaches the destination node 103 at time t10. Normally, since the reception processing of the first packet signal 51 has been completed,
The transfer destination node 103 can receive the second packet signal 65.

The transfer destination node 103 receives the second packet signal 65 and, at time t11, sends a second acknowledgment complete signal 81 indicating that the reception of the second packet signal 65 was successful, to the transfer source node 101. Reply to.

At time t12, transfer source node 101 receives second acknowledgment complete signal 81.

In the transfer destination node 103, the reception processing T12 of the second packet signal 65 is performed, for example, at time t.
Starts at 11.

By using the control circuit C including the delay time providing circuit as described above, the probability that the busy acknowledge signal is returned again for the packet signal retransmitted after the transfer source node receives the busy acknowledge signal Becomes lower.

As described above, when the data communication apparatus according to the present embodiment is used, the busy acknowledge signal and the retransmission packet signal are repeatedly transferred between the transfer source node and the transfer destination node. Congestion can be eliminated.

In the asynchronous transfer, it is possible to reduce the number of repetition steps of the busy acknowledge signal and the retransmission of the packet signal, thereby preventing an increase in signal traffic.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments. Various choices can also be made regarding the configuration of the control circuit and the like.
It will be obvious to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0115]

According to the present invention, it is possible to eliminate congestion on the bus line due to the repetitive transfer of the busy acknowledge signal and the retransmission data signal on the bus line connecting the transfer source node and the transfer destination node.

[Brief description of the drawings]

FIG. 1 shows a configuration example of a communication network using an interface based on the IEEE 1394 standard.

FIG. 2 is a conceptual diagram for explaining a step of determining a node number (self ID) in the configuration example of the communication network shown in FIG.

FIG. 3 is a conceptual diagram for explaining a bus use right requesting step in the configuration example of the communication network shown in FIG. 1;

FIG. 4 describes a step of sending a bus license or a DP (data prefix) packet in the configuration example of the communication network shown in FIG.

FIG. 5 is a specific traffic diagram relating to packet communication using asynchronous data transfer in a communication network using an interface based on the IEEE 1394 standard.

FIG. 6 is a functional block diagram showing a configuration of a control circuit provided in each node of the data communication device according to one embodiment of the present invention.

7 is a functional block diagram of a delay time providing circuit which forms a part of the control circuit shown in FIG. 6;

FIG. 8 is a timing chart illustrating an operation of the delay time providing circuit.

FIG. 9 is a specific traffic diagram when the data communication device according to the embodiment of the present invention is used.

[Explanation of symbols]

 C control circuit BPL bypass line transfer source node 1, 101 transfer destination node 3, 103 33 busy acknowledge signal detection circuit 35 delay time provision circuit 37 data signal retransmission circuit 47 delay time setting register 48 counter 50 comparator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 12/40 H04L 11/00 320 F term (Reference) 5B077 AA17 AA34 FF11 GG06 GG15 NN02 5B089 GB01 HA17 HA18 JB06 KE02 KF03 MA04 5K032 AA01 AA02 BA01 BA16 CC04 DA06 5K033 AA01 AA02 BA01 BA15 CB04 DA05 DA13 5K034 AA01 CC02 DD03 HH65 MM03 QQ09

Claims (6)

[Claims] 1. A plurality of nodes each including a control circuit for performing transmission / reception processing of a data signal, and a plurality of communication cables for serially connecting the respective nodes, wherein a data signal is transmitted in the control circuit. When receiving a busy acknowledge signal for notifying the transfer source node that a data signal transmitted toward the transfer destination node receiving a data signal from the transfer source node cannot be received at the transfer destination node, A data communication device comprising a delay time providing circuit for delaying a retransmission time from when the busy acknowledge signal is received to when the same data signal is retransmitted from the source node to the destination node. 2. The method according to claim 1, wherein the delay time providing circuit in the control circuit transmits a first data signal transmitted from a source node transmitting the data signal to a destination node receiving the data signal at the destination node. An acknowledgment signal indicating the reception is transferred to the transfer source node, and subsequently, the second data signal transmitted from the transfer source node to the transfer destination node cannot be received by the transfer destination node. When receiving the busy acknowledge signal for notifying the transfer source node, from when the busy acknowledge signal is received to when the same second data signal is retransmitted from the transfer source node to the transfer destination node. 2. The data communication apparatus according to claim 1, wherein a retransmission time is delayed. 3. A busy acknowledge signal detecting circuit for outputting a busy acknowledge signal to the delay time providing circuit when the busy acknowledge signal is detected in the control circuit; A data signal retransmitting circuit for retransmitting the same data signal toward the transfer destination node after receiving a delayed busy acknowledgment reception signal obtained by adding a delay time to the acknowledgment signal in the delay time providing circuit. 3. The data communication device according to 1 or 2. 4. The delay time setting circuit, wherein the delay time setting circuit stores the retransmission time, a counter circuit that starts counting when the busy acknowledge reception signal is received, and an output of the delay time setting circuit. 4. The data communication apparatus according to claim 3, further comprising: a comparator that compares an output of the counter circuit and outputs the delayed busy acknowledgment reception signal to which a delay time is added when the values of both outputs match. 5. A data communication apparatus comprising: a plurality of nodes each including a control circuit for performing transmission / reception processing of a data signal; and a plurality of communication cables (bus lines) for serially connecting the nodes. a) transmitting a data signal from a source node transmitting the data signal to a destination node receiving the data signal; and b) indicating that the source node failed to receive the data signal to the source node. Pausing the retransmission of the data of the source node during a predetermined pause period starting from the time when the busy acknowledgment signal is received, when the source node receives the busy acknowledge signal notifying the node; c) Retransmitting the data signal from the source node to the destination node again after the end of the pause period. . 6. A data communication apparatus comprising: a plurality of nodes each including a control circuit for performing transmission / reception processing of data signals; and a plurality of communication cables for serially connecting the nodes. Transmitting a first data signal from a source node that transmits a data signal to a destination node that receives a data signal; and b) the first data signal transmitted toward a destination node that receives a data signal. Transferring the acknowledgment signal from the destination node to the source node when the destination node receives the acknowledgment signal from the destination node; and c) following the step b) from the source node to the destination node. Transmitting a second data signal to the node; d) indicating that the destination node failed to receive the second data signal. E) suspending data retransmission during a predetermined pause period starting from when the busy acknowledge signal is received by the transfer source node when the transfer acknowledge node receives the GACK signal; Retransmitting the second data signal from the source node to the destination node.