JPH09298578A - Method and system for insuring data for digital communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To insure the data of synchronous communication without interrupting any communication by storing data, which are transmitted by a transmission node, in the prescribed address information of a buffer in the state of enabling mapping of time information and address information. SOLUTION: Each node (communication equipment) consisting a network is provided with an LSI 5 for communication equipped with a clock generating circuit 6 for counting bus time, a CPU 1 and a buffer memory 2 for data insurance or the like. In this case, the transmission node transmits data through the protocol of synchronizing system and stores these data in the buffer 2. When the reception node can not normally receive them, the time information at such a time is mapped into the address information and returned to the transmission node through the protocol of asynchronous system and the retransmission of data is requested. Based on this address information, the transmission node reads data out of the buffer 2 and retransmits the read data through the protocol of asynchronous system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital communication, and more particularly to a technique for ensuring data to be communicated.

[0002]

2. Description of the Related Art Conventionally, video equipment and audio equipment are provided with input / output terminals for analog signals, and video signals and audio signals are communicated between the equipment in analog form.

In recent years, digital communication has become popular in place of analog communication. A representative standard for digital communication is I
It is defined by EEE1394. FIG. 13 shows the IEEE
An example of 1394 isochronous communication is shown.

Isochronous communication takes time T (= 125
It is synchronous communication performed at intervals of μs). The communication cycle time is T. Within the cycle time T, the cycle start packet SP, the packet header PH and the data DT
Are supplied to the bus as a set.

The cycle start packet SP is a signal supplied from the root node in the communication network and permitting the start of communication. The communication device, after detecting that the cycle start packet SP is supplied to the bus,
Packet header PH and data DT without specifying the communication partner
To the bus. The packet header PH is a header in which the data length of the communication data DT and the like are described. Data D
T is data to be communicated such as a video signal.

In isochronous communication, since a predetermined bandwidth is secured at intervals of time T, real time communication is possible. When the communication device on the transmission side detects the cycle start packet SP, it broadcasts the packet header PH and the data DT to the bus without specifying the communication partner. The communication device on the receiving side fetches the packet header PH and data DT supplied to the bus as necessary. The communication device on the transmission side keeps sending the packet header PH and the data DT, and cannot know whether or not the communication device on the reception side normally receives them.

[0007]

Isochronous communication is basically synchronous communication that does not guarantee data.
The data transmitted by the communication device on the transmission side is equivalent to the broadcast message and does not undergo handshake with the communication device on the transmission destination, so it is not possible to confirm whether or not the communication partner has normally received.

However, for example, when communicating compressed image data, there is a high possibility that data loss or garbled data will cause fatal damage, and means for guaranteeing communication data is desired. In isochronous communication, when a communication error occurs, it cannot be known, so data cannot be guaranteed.

An object of the present invention is to provide a data guarantee method capable of guaranteeing data for synchronous communication without interrupting communication. Another object of the present invention is to provide a data guarantee system capable of guaranteeing data for synchronous communication without interrupting communication.

[0010]

A data guarantee method according to the present invention is a data guarantee method in a digital communication network for connecting a transmitting node for transmitting data and a receiving node for receiving transmitted data. The step of transmitting data by a synchronous protocol and accumulating the transmitted data in a buffer, and when the receiving node cannot receive the transmitted data normally, the transmitting node can receive the data normally. A step of acquiring time information when there is no data, mapping the time information to address information, returning the address information to a transmitting node by an asynchronous protocol, and requesting retransmission of data that could not be normally received; When the node receives the address information, it reads data from the buffer based on the address information and reads it. The data and the step of retransmitting asynchronously protocol.

The transmitting node transmits data by a synchronous protocol and stores the transmitted data in a buffer. The address information of the buffer corresponds to the time information. The receiving node acquires the time information when it cannot be normally received and maps the time information to the address information. The address information identifies the data for which retransmission is requested. The receiving node identifies the data using the address information and requests retransmission by using an asynchronous protocol. When the sending node receives the resend request from the receiving node, it reads the data from the buffer based on the address information, and resends the data to the receiving node by the asynchronous protocol. The receiving node receives the retransmission data.

Further, the data guarantee method of the present invention is a data guarantee method in a receiving node for receiving data in a digital communication network, in which the receiving node receives data transmitted from outside by a synchronous protocol. When the data cannot be received normally, the time information at the time when the data cannot be received normally is acquired, the time information is mapped to the address information, the address information is returned by the asynchronous protocol, and the data cannot be received normally. Requesting retransmission of the.

The data guarantee system of the present invention transmits data by a synchronous protocol, stores the transmitted data in a buffer, and receives a resend request including address information from the outside, and based on the address information. Means for reading data from the buffer and retransmitting the read data by an asynchronous protocol, a receiving means for receiving the data by a synchronous protocol, and a normal reception when the receiving means cannot receive normally. And means for acquiring time information when it was not possible, mapping the time information to address information, returning the address information to the outside by an asynchronous protocol, and requesting retransmission of data that could not be normally received. .

The data guarantee system of the present invention is
Receiving means for receiving data by a synchronous protocol, and when the receiving means cannot receive normally,
It has means for acquiring time information at the time of unsuccessful reception, mapping the time information to address information, returning the address information by an asynchronous protocol, and requesting retransmission of data that could not be normally received. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 shows an I according to an embodiment of the present invention.
The structure of a communication network of the EEE1394 standard is shown.

The network is constructed by connecting five nodes (communication devices) ND1 to ND5 to the bus. A node ID (identifier) is set to each node ND. The node ID is, for example, 1 for the node ND1, 2 for the node ND2, 3 for the node ND3, 4 for the node ND4,
The node ND5 is 5. Among these, the node ND having the largest node ID becomes the root node. The root node is, for example, the node ND5.

FIG. 3 shows an example of the configuration of one of the five nodes shown in FIG. The node is a communication LSI (large-scale integrated circuit) 5 for performing processing relating to communication.
, A CPU 1, a ROM 3, a RAM 3, and a data guarantee buffer memory 2, which are connected to each other via a local bus 8.

The ROM 3 stores various parameters and computer programs. The CPU 1 performs calculation and control according to a computer program stored in the ROM 3. The RAM 4 has a working memory of the CPU 1 including registers and buffers. The buffer memory 2 and the RAM 4 may be composed of the same memory.

The communication LSI 5 has a clock generation circuit 6 for counting the bus time and a communication connector 7 for connecting to another node. Although the bus time is basically counted based on the node's own clock generation circuit 6, since it is used as common time information by all nodes connected to the network, the root node is used for each cycle of isochronous communication. It is modified to match the bath time of.

The root node supplies the cycle start packet SP (FIG. 13) to the bus at the beginning of one cycle. The bus time of the root node is described in the cycle start packet SP. Each node receives the cycle start packet SP and corrects its own bus time to match the bus time. Therefore, all nodes can share the same bus time.

The communication LSI 5 has, in addition to the clock generation circuit 6 and the communication connector 7, buffers for buffering transmission data and reception data, respectively. The data guarantee buffer memory 2 stores the transmitted data for a certain period of time in order to guarantee the data by the isochronous communication. At that time, the data transmitted to a predetermined address of the buffer memory 2 is stored in association with the time information.

When the receiving node cannot perform normal reception, the transmitting node transmits the transmission data stored in the data guarantee buffer memory 2 to the receiving node again in response to the request from the receiving node, and the data is transmitted. Make a guarantee.

FIG. 1 shows an example of communication according to this embodiment.
The transmitting node transmits data by isochronous communication with time T (= 125 μs) as one cycle. For example, at time t1, the root node supplies a cycle start packet SP for permitting the start of communication to the bus. After detecting the cycle start packet SP, the transmitting node supplies the data D1 to the bus without specifying the communication partner.

The data D1 includes a packet header PH and data DT. The packet header PH is the communication data DT
It is a header in which the data length of is described. Data DT
Is data to be communicated such as a video signal.

Thereafter, the transmitting node supplies the data D2 to the bus at the cycle of time t2, the data D3 at the cycle of time t3, the data D4 at the cycle of time t4, and the data D5 at the cycle of time t5. Isochronous communication
Since the data D having a predetermined data amount can be transmitted at intervals of time T, the data can be transmitted in real time.

The transmission of the transmitting node does not specify the communication partner. Therefore, a plurality of receiving nodes can receive the same data. The receiving node determines the type of transmission data based on the contents of the packet header PH and fetches the data D as needed.

In order to guarantee the transmitted data, the transmitting node allocates the transmitted data to the address space defined by the IEEE1212 standard (hereinafter referred to as 1212 address).
To memorize. The 1212 address is an address space based on the communication of the IEEE 1394 standard.

FIG. 4 shows the structure of 1212 addresses.
The 1212 address is composed of 64 bits, and in order from the higher order, a 10-bit bus ID and a 6-bit node I.
D, consisting of a 48-bit offset value. Since the 1212 address includes the 6-bit node ID, the node can be specified by designating the 1212 address.

The 1212 address is an address in the virtual memory address space and it is not necessary to actually implement the entire memory space. All the nodes configuring the network can commonly use the 1212 address space.

Returning to FIG. 1, times t1, t2, t3, t
Since 4 and t5 are time information, each can be represented by a bus time value. The transmitting node uses the data D1, D
The time at which 2, D3, D4 and D5 are transmitted can also be represented by a bus time value. If the bus time value at the start of transmission and the 1212 address value are associated with each other, the transmitted data can be stored in the 1212 address space corresponding to the bus time. The mapping between the 1212 address space and the bus time value can be easily done.

The time when the receiving node receives the data is delayed by the transmission time from the time when the transmitting node transmits the data. However, the bus time based on the transmission start time is the same as the bus time based on the reception start time. The receiving node records the bus time value at the start of reception, so that the data D1, D2, D3, D4, D
It is possible to know the position in the 1212 address space where 5 is stored.

In order for the receiving node to obtain the reception start bus time value, for example, the packet header PH in the data D received by isochronous communication may be used. FIG.
Shows the structure of the packet header PH. The packet header PH is composed of 32 bits, and among the 32 bits, the most significant 16 bits are an area for describing the data length of the communication data DT, and the least significant 4 bits are a sync bit that the user can arbitrarily use. This sync bit is used.

The transmitting node sets the sync bit of the packet header PH to 1 for the first data to be transmitted, and transmits the subsequent data with the sync bit of the packet header PH to 0.

The receiving node receives the packet header P
Check H sync bit. If the sync bit is 1, it is determined that the data is the reception start data, and the bus time value at that time is acquired. The bus time value indicates the communication start timing.

Next, a method of guaranteeing data when the receiving node causes a reception error for the data D1 will be described.
As shown in FIG. 1, when the receiving node fails to receive the data D1, the receiving node is asynchronous.
In communication, for example, the data RQ1 is returned to the transmitting node between the times t3 and t4, and the retransmission of the data D1 is requested.

Asynchronous communication will be described. I
The EEE1394 standard permits the coexistence of two types of communication, synchronous isochronous communication and asynchronous asynchronous communication. Asynchronous communication is performed asynchronously by isolating the isochronous communication so as not to limit the communication bandwidth of the isochronous communication and specifying the communication partner.

Retransmission request data RQ1 is specified by the 1212 address, not by specifying the packet number of the communication when specifying the data D1 for which retransmission is requested.

FIG. 6 shows an example of the structure of the retransmission request data RQ1. In isochronous communication, a communication destination is specified and communication is performed. The retransmission request data RQ1 includes, for example, a transmission destination (retransmission request destination node), a requester of the message RQ1 (own node), an offset value of 1212 address (FIG. 4), and a data length to request retransmission (1 packet. Data length) and a read request R.

The transmitting node receives the data RQ1 and receives the data D from the data guarantee buffer memory 2 (FIG. 3) according to the 1212 address designated in the data RQ1.
Read 1. Then, as shown in FIG. 1, the data D1
Data RP1 including, for example, from time t5 to t
Asynchronous communication is performed during 6 to retransmit to the receiving node.

FIG. 7 shows an example of the structure of the retransmission request response data RP1. The resend request response data RP1 includes a header 21 and data 22. The data 22 is data to be retransmitted. The header 21 includes, for example, a transmission destination (retransmission request source node), a requester of the message RP1 (own node), an offset value of 1212 address (FIG. 4),
The retransmitted data length (data length of the data 22) and the write request W are included.

The receiving node receives the resend request response data R
1212 specified in the data RP1 after receiving P1
The retransmitted data 22 is overwritten in its own reception error area indicated by the address.

FIG. 8 is a flowchart showing the transmitting operation of the transmitting node. At step SA1, one packet is transmitted by isochronous communication. After receiving the cycle start packet SP (FIG. 1), the transmitting node extracts one packet of data from the transmission data buffer memory 2 (FIG. 3), attaches the packet header PH to the data DT, and transmits it. For example, the data D1 shown in FIG. 1 is transmitted.

As shown in FIG. 9, the transmission data 12a, 1
Data 2b and 12c are data shown in the 1212 address space, and are stored in, for example, the RAM 4 (FIG. 3) or a hard disk. The 1212 address space corresponds to the bus time axis. First, in the buffer memory 2,
Part of the data 12a at the head is loaded, and data is guaranteed even after transmission, so the data is not erased and remains. The transmission data 12a may be loaded into the real address space of the buffer memory 2 and then the transmission data 12a may be mapped into the 1212 address space.

Returning to FIG. 8, in step SA2, it is checked whether or not the contents of the buffer memory 2 need to be changed. If all the contents of the buffer memory 2 have been transmitted, it is necessary to change the contents of the buffer memory 2, so the flow proceeds to step SA3.

At step SA3, the contents of the buffer memory 2 are switched. As shown in FIG. 9, for example, when the data 12a is stored in the buffer memory 2,
The next data 12b is transferred from the RAM 4 to the buffer memory 2 by direct memory access (DMA), for example. The first half of the next data 12b is the previous data 12a
It overlaps with the latter half. Transmission is performed only for the rear half of the next data 12b. The overlapping portion of the data 12a and 12b is the data that has already been transmitted, and by leaving it in the buffer memory 2, it is possible to respond to the retransmission request from the receiving node. The amount of data in the overlapping portion is the minimum amount of data guaranteed.

Each time data is passed through step SA3, data 1
The contents of the buffer memory 2 are switched while shifting the data by half in the order of 2a, 12b, 12c. Thereafter, the flow advances to Step SA4.

Returning to FIG. 8, when it is not necessary to change the buffer memory 2 in step SA2, that is, when untransmitted data remains in the buffer memory 2, the contents of the buffer memory 2 are not switched and step SA4 is performed. Go to.

At Step SA4, it is checked whether or not the transmission of all data has been completed. If the transmission of all data has not been completed, the process returns to step SA1 and the transmission is repeated for the next packet. When the transmission of all the data is completed, the process ends.

FIG. 10 is a flowchart showing the receiving operation of the receiving node. In step SB1, necessary items (transmission conditions) shown below are obtained from the transmission node in asynchronous communication as initial settings before starting communication. The transmission node sets the transmission condition on the RAM 4 (FIG. 3) and maps it on the 1212 address. The receiving node reads out the transmission condition on the 1212 address by asynchronous communication.

(1) Start Timing The transmitting node sets the bus time scheduled to start transmission on the 1212 address. The receiving node acquires the start timing by reading the bus time by asynchronous communication. The start timing indicates which position on the time (bus time) axis the first packet corresponds to. The receiving node maps between the bus time and the 1212 address based on this start timing.

Further, as described above, the sync bit (FIG. 5) in the packet header PH received by the isochronous communication is checked, and if the sync bit is 1, it means that the data is transmission start data. The bus time at that time can also be used as the start timing.

(2) Start address The transmission data is stored 121 in order to know which position in the 1212 address space the bus time value corresponds to.
2 Get the start address in the address space. This start address indicates to which position on the address space axis the position of the start timing (1) on the time axis is mapped.

(3) Packet size and total data size The packet size is the size (data length) of one packet in isochronous communication. For example, the size is one data DT shown in FIG. The total data size is the total data size transmitted by isochronous communication.

The total data size / packet size indicates the number of packets, that is, the number of times isochronous communication is performed. The end timing can be calculated by acquiring this number of times. Processing for guaranteeing communication data is performed from the start timing to the end timing.

(4) Number of Data Guarantee Packets The number of data guarantee packets is the number of packets when a certain packet is transmitted.
It shows how many packets before that can respond to the data retransmission request, and corresponds to the data length of the overlapping portion of the data 12a and the data 12b shown in FIG.

Returning to the flowchart of FIG. 10, in step SB2, real-time reception by isochronous communication is performed. This reception is the reception of one packet. For example, the data D1 shown in FIG. 1 is received.

At step SB3, it is checked whether or not the reception is normally performed. When the reception is normally performed, the process proceeds to step SB4. In step SB4, it is checked whether all data has been received, that is, all packets have been received. When all the packets have not been received, the process returns to step SB2 and the real-time reception of the next packet is repeated. When all the packets have been received, the processing ends.

If it is determined in step SB3 that the signal was not received normally, step SB5
Then, the recover task is started to request the resend. The process of the recover task will be described later with reference to FIG. Then, the process returns to step SB2 to repeat the real-time reception of the next packet.

FIG. 11 is a flow chart showing details of the recover task in step SB5 of FIG.
At step SC1, address conversion of an abnormal cycle is performed. The receiving node acquires the bus time when the reception is not normally performed, and calculates the 1212 address from the difference between the bus time and the start timing (bus time at the start of transmission).

In step SC2, the transmission node is instructed to read the data of the calculated 1212 address, and a retransmission request is issued. For example, as shown in FIG. 1, retransmission request data R
Q1 is transmitted by asynchronous communication. After that, the process ends. The transmitting node receives this and performs the following processing.

FIG. 12 shows that the transmitting node sends retransmission request data R
This is the process when Q1 is received. In step SD1, it is checked whether or not the target data of the resend request is in the memory buffer 2. The target data is designated by the 1212 address. If the target data is in the memory buffer 2, the process proceeds to step SD2.

At step SD2, the target data is read from the buffer memory 2 and retransmitted to the receiving node. For example, as shown in FIG. 1, the retransmission request response data RP1 is transmitted by asynchronous communication. After that, the process ends.

When it is determined in step SD1 that the target data is not in the buffer memory 2, step S
Proceed to D3. In step SD3, an error code is returned by asynchronous communication in order to notify that the target data cannot be retransmitted. After that, the process ends.

As described above, the transmitting node stores the transmitted data in the memory buffer for the number of data guarantee packets or more. By setting the time information (bus time) and the address information (1212 address) in a mappable state, the receiving node does not specify the packet number at the time of a reception error, but by specifying the address, Requests resending of data that could not be received normally. That is, the receiving node makes a retransmission request to the address space.

For normal data, data communication is performed by synchronous communication (synchronous communication). On the other hand, since the resend request and its response are performed by asynchronous communication (asynchronous communication), even if a resend request is made, the bandwidth of the synchronous communication is not limited, and data is guaranteed without interrupting the synchronous communication. You can Furthermore, even if the synchronous communication is a protocol without handshake, the data can be guaranteed.

When the transmitting node transmits certain data, not all the nodes constituting the network may receive a reception error. In some cases, only some nodes may cause a reception error. According to this embodiment, only the receiving node that has caused a reception error can make a retransmission request. Even when a plurality of receiving nodes cause a reception error and each of them makes a retransmission request, the transmitting node can respond to each of those requests.

Although the transmitted data is stored in the buffer memory, it is sufficient to store more than the data corresponding to the time until the reading from the buffer memory is completed in response to the transmission request.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0069]

As described above, according to the present invention,
By setting the time information and the address information in a mappable state and storing the data transmitted by the transmitting node in the predetermined address information of the buffer, the receiving node can determine the number of times when it cannot receive normally. It is possible to request retransmission of data by designating an address instead of designating.

Since the retransmission request and the retransmission are performed by the asynchronous protocol, the data guarantee can be performed without interrupting the communication by the synchronous protocol.

[Brief description of drawings]

FIG. 1 is a diagram showing communication data according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an IEEE 1394 standard communication network according to the present embodiment.

FIG. 3 is a block diagram showing a configuration example of one node among the five nodes shown in FIG.

FIG. 4 is a diagram showing a structure of an IEEE1212 address.

FIG. 5 is a diagram showing a structure of a packet header PH.

FIG. 6 is a diagram showing a configuration example of retransmission request data RQ1 shown in FIG.

FIG. 7 is a diagram showing a configuration example of retransmission request response data RP1 shown in FIG.

FIG. 8 is a flowchart showing a transmitting operation of a transmitting node.

FIG. 9 is a diagram showing a data guarantee buffer memory in which transmission data is accumulated.

FIG. 10 is a flowchart showing a receiving operation of a receiving node.

11 is a flowchart showing details of a recover task in step SB5 of FIG.

FIG. 12 is a flowchart showing processing when the transmitting node receives retransmission request data RQ1.

FIG. 13 is an IEEE1394 isochronous (isochr)
FIG. 3 is a diagram showing an example of onous) communication.

[Explanation of symbols]

 1 CPU 2 Data guarantee buffer data 3 ROM 4 RAM 5 Communication LSI 6 Clock generation circuit 7 Communication connector 8 Local bus

Claims (4)

[Claims] 1. A transmitting node for transmitting data,
A data guarantee method in a digital communication network for connecting a receiving node for receiving transmitted data, the transmitting node transmitting data by a synchronous protocol and accumulating the transmitted data in a buffer. And, when the receiving node cannot normally receive the transmitted data, obtains time information at the time when it cannot be normally received, and maps the time information to address information,
A step of returning the address information to the sending node by an asynchronous protocol and requesting resending of the data that could not be normally received; and when the sending node receives the address information, the data is sent from the buffer based on the address information. A data guarantee method including a step of reading and retransmitting the read data by an asynchronous protocol. 2. A method of guaranteeing data in a receiving node for receiving data in a digital communication network, wherein when the receiving node cannot normally receive data transmitted from outside by a synchronous protocol, It includes a step of acquiring time information at the time of unsuccessful reception, mapping the time information to address information, returning the address information by an asynchronous protocol, and requesting retransmission of data that could not be normally received. Data guarantee method. 3. A means for transmitting data according to a synchronous protocol, storing the transmitted data in a buffer, and receiving a resend request including address information from the outside, transmitting the data from the buffer based on the address information. reading,
A means for retransmitting the read data by the asynchronous protocol, a receiving means for receiving the data by the synchronous protocol, and a time information when the receiving means is not normally received, when the receiving means is not normally received. A data assurance system in digital communication, comprising means for acquiring, mapping the time information to address information, returning the address information to the outside by an asynchronous protocol, and requesting retransmission of data that could not be normally received. 4. Receiving means for receiving data by a synchronous protocol, and when the receiving means cannot normally receive, time information at the time of unsuccessful reception is acquired and the time information is used as address information. A data assurance system in digital communication, which has means for mapping the address information to an asynchronous protocol and returning the address information by an asynchronous protocol to request retransmission of data that cannot be normally received.