JPH10200573A - Data transmitting method, data transmission format and data transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit instructions to a data sending end with a sure timing, when flow control is applied on a data receiving end by previously securing a band of isochronous transfer for flow control from a device at a receiving end to a device at a sending end, when data transfer starts from the device at a sending end to the device at a receiving end. SOLUTION: Isochronous packets 102 and 107 use a channel (i) to transfer certain data 1 from a device at a specific sending end to a device at a specific receiving end. Isochronous packets 103 and 108 have been previously secured as a channel (j) at the time of starting data transfer, to control flow of transfer of the data 1 between the devices. That is, although the isochronous packets for controlling the flow transfer empty packets, when an instruction for controlling the flow is sent, the instruction is superimposed on the isochronous packets and then are sent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method between AV devices and computer devices when the devices are connected by a digital interface (for example, IEEE1394) having an isochronous transfer function.

[0002]

2. Description of the Related Art Among digital interfaces for connecting AV equipment and computer equipment, for example, IEEE 13
Reference numeral 94 denotes two types of data transfer modes, namely, asynchronous (asynchronous) transfer and isochronous (synchronous) transfer, and enables high-speed transfer from 100 Mbit / sec to 400 Mbit / sec.

[0003] Isochronous transfer is a transmission method in which a band is secured in advance between a plurality of data transmission devices that transmit and receive data and a transmission delay is guaranteed.

[0004] The isochronous transfer is for transferring multimedia data such as a moving image and a sound, and secures a transfer speed for multimedia data transfer in advance to enable real-time data transfer.

On the other hand, asynchronous data transfer is used for data transfer that does not require real-time processing. These transfers are
The cycle is performed every 125 μsec. The isochronous transfer is performed in the first half of each cycle, and the asynchronous transfer is performed in a time remaining after the isochronous transfer. That is, the isochronous transfer is executed prior to the asynchronous transfer. Note that there is a limit to the ratio occupied by each transfer mode in one cycle, and a maximum of 1024 bytes for 100 Mbit / sec in isochronous transfer
te is about 2/3 of one cycle, and the maximum is 63.5 μsec for asynchronous transfer.

In the isochronous transfer, it is necessary to obtain a band to be used in one cycle from a node that manages the band before the transfer in order to guarantee a constant transfer speed. A node is assigned to each device on the network. The function to manage the bandwidth
Exists at the node of the device that is the master on the network. In isochronous transfer, data can be transferred within the band secured by this node.

When data is recorded on a drive having a variable transfer rate such as a DVD (digital video disk) drive, if the transfer speed of the isochronous transfer is set to a certain speed or higher, or if a fixed transfer rate is received. If the fixed transfer rate of the device is lower than the transfer speed of the isochronous transfer, transmitted data may not be able to be received by the device on the receiving side in some cases.

[0008] Therefore, in order to prevent the receiving device from becoming unable to receive data, it is necessary to perform flow control for controlling data transfer from the receiving device to the data transmitting device. For this purpose, commands such as start and stop of data transfer are sent to the data transmitting device by asynchronous transfer.

[0009]

As described above, in asynchronous transfer and isochronous transfer, isochronous transfer is performed with priority over asynchronous transfer which is asynchronous transfer. Then, when transferring data in a certain unit called a packet in each cycle, the asynchronous transfer has a lower priority than the isochronous transfer, or all the asynchronous packets are temporarily occupied by another data. Sometimes
The transfer may not be possible in the desired cycle.

FIG. 4 is a diagram showing a conventional method of using packets for each cycle using flow control by asynchronous transfer. In FIG. 4, reference numerals 401 and 405 denote cycle start packets, which are transferred when a cycle starts. Reference numerals 402 and 406 denote isochronous packets, and reference numerals 403 and 407 denote asynchronous packets.

Note that these packets are each 1 for convenience.
Although it is illustrated as if it were one packet, it is actually divided into several packets, and is conceptually described as only one packet. 404,
Reference numeral 408 denotes a response that is always returned in response to the transfer of the asynchronous packet, and indicates an operation of transmitting a code ack and confirming the result of the data transfer.

Here, the isochronous packet 402,
Suppose that 406 is transferring certain data 1 from a specific transmitting device to a specific receiving device using channel i. It is assumed that the asynchronous packet 407 transfers a command for controlling the flow of data 1 transfer. The asynchronous packet 403 transfers certain data 2 between devices irrelevant to the transfer of data 1 between those devices.

As shown in FIG. 4, even if an asynchronous packet 407 for controlling the flow of data 1 which has been isochronously transferred is sent in cycle m, another asynchronous packet 403 already has a transfer priority and is asynchronous. If the transfer bandwidth is occupied, it cannot be sent in that cycle. In FIG. 4, the transfer right is given to the asynchronous packet 407 for flow control in the cycle m + 1, and the transfer is executed. However, if another asynchronous transfer with a higher priority already exists, the flow control is further performed. Executable cycles will be delayed. In that case, the isochronous transfer of the data 1 continues during that time, which may result in exceeding the buffer capacity of the receiving side.

[0014]

SUMMARY OF THE INVENTION In view of the above problems, the present invention makes it possible to transmit an instruction to a data transmitting side at a reliable timing when a data receiving side intends to perform flow control. Things.

According to the first aspect of the present invention, there is provided a data transmission method for controlling a flow from a receiving device to a transmitting device when data transfer from a transmitting device to a receiving device is started in advance. This is to secure a transfer band.

According to a second aspect of the present invention, a band for data transfer and a band for flow control of the data transfer are collectively reserved, and a band for data transfer and a band for flow control are selected from the band as needed. Is assigned.

The data transmission device according to claim 13 is
According to the amount of data stored in the reception buffer of the receiving-side device, an instruction to control the flow of data is transmitted to the transmitting-side device by isochronous transfer.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a data transmission method according to a first embodiment of the present invention. In FIG. 1, 101 and 106 are cycle start packets, 10
Reference numerals 2, 103, 107, and 108 denote isochronous packets, 104 denotes an asynchronous packet, and 105 denotes a response for an asynchronous packet.

It is assumed that the isochronous packets 102 and 107 transfer certain data 1 from a specific transmitting device to a specific receiving device by using the channel i.
The isochronous packets 103 and 108 are used to control the flow of data 1 transfer between those devices.
This is reserved in advance as channel j at the start of data transfer. That is, when there is no need to control the flow, the isochronous packet for flow control transfers an empty packet, but when an instruction to control the flow is to be sent, the instruction is carried on this isochronous packet.

That is, if an attempt is made to send a flow control instruction in a certain cycle m, the transmission of the instruction can be reliably executed in that cycle, and the transfer of data 1 by an isochronous packet can be controlled.

(Second Embodiment) FIG. 2 is a diagram showing a data transmission method according to a second embodiment of the present invention. In FIG. 2, reference numerals 209 and 210, which are different from those in FIG. 1, denote units for managing packets for data transfer and packets for flow control collectively as a set.

That is, the second embodiment differs from the first embodiment in that the bandwidth for data transfer and the bandwidth for flow control are totaled and secured once at the start of data transfer. The secured band is managed as one set. Then, in one set, two channels and a band for each channel are allocated for data transfer and flow control. The header area of each packet for data transfer and flow control indicates a flag area for distinguishing whether the packet is for data transfer or flow control, and a set number indicating that the packet is a set. Add an area.

FIG. 3 shows a conventional CIP (Common Isochronous Pac) located before the data portion of an isochronous packet.
FIG. 7 is a diagram showing an example of adding these two new areas to a (ket) header.

In FIG. 3, the SID 301 is an ID assigned to specify a node of a device that transmits a packet.
D. DBS 302 is a unit of size when packetizing transmission data, and FN 303 is the number of divisions when packetizing transmission data. 304 QPC
Indicates the size of dummy data added to the transmission data when the transmission data is divided into packets. 305 SPH
Is a flag indicating the presence or absence of a packet header.
RSV is an area for future expansion.

The DBC 307 is a packet counter for detecting packet loss, and the FMT 308 is an ID representing a data format such as MPEG (Moving Picture Experts Group). 309 DF,
This is a 1-bit flag that distinguishes whether the packet transfers data or controls the flow. For example, D
When F is 0, the packet indicates flow control, and when DF is 1, the packet indicates data transfer.

The SET 310 is an area for designating the same set number for data transfer and flow control corresponding to each other. Since the set number is defined as two channels as one set, if the number of channels is 64 as in IEEE1394, the set number is 32.
A type, that is, 5 bits is sufficient. The FDF 311 is an area to which necessary information is added according to the data format defined by the FMT 308.

By using the newly defined CIP header, when a command request is issued between data transmission devices or from another device, the direction of data transfer and flow control is switched in the opposite direction. Can be easily handled. That is, in this case, the devices that perform the data transfer and the corresponding flow control are switched, so that the SID 301 of the data transfer and the corresponding flow control packet may be replaced with each other, and the channel and bandwidth to be used may be replaced. Does not need to be changed.

When the isochronous transfer is performed, an area indicating the channel in which the transfer is being performed is located before the CIP header, that is, in an area called a packet header at the head of each packet.
In order to specify a set of data transfer and flow control corresponding thereto, instead of using the SET 310, an area in which a channel can be specified may be secured and the channel number of the partner flow in the same set may be indicated.

Alternatively, instead of using the SET 310, a set of corresponding data and flow control can be specified by indicating a node ID of a device that receives a packet to be transferred. This is because the CIP header of each packet originally has SID 301 which is the node ID of the node transmitting the packet.
Is added, if the one indicating the receiving node ID of the packet of another flow matches the SID 301, it is understood that they correspond to each other.

Alternatively, in the FMT 308, which is an area indicating the type of data, a corresponding set of data transfer and flow control can be specified by using the method described above. For example, in FIG. 3, the FMT 308 is replaced with the DF 309 and the SET 310, and the FDF including the original DF 309 and the SET 310 is replaced.
311.

(Third Embodiment) FIG. 5 is a diagram showing a data transmission apparatus according to a third embodiment of the present invention. In FIG. 5, reference numeral 501 denotes a host controller that controls the entire data transmission device, and 502 denotes a host interface that exchanges commands with the host controller.
Reference numerals 503, 504, and 505 denote buffers for storing data. Reference numeral 503 denotes data to be transferred asynchronously.
4 is data for isochronous transfer, and 505 is for storing received data.

Reference numeral 506 denotes a flow control means for controlling data transfer according to the amount of data stored in the reception buffer. 511 is a cable, and 510 is a cable 511
Is a physical layer to be connected, 509 is a physical interface for exchanging commands with the physical layer, 507 is a transmitter for transmitting data stored in the transmission data buffer 503 or 504 to the physical interface 509, and 50
Reference numeral 8 denotes a receiver that sends data received from the physical interface 509 to a reception buffer.

When the data stored in the reception buffer 505 of the receiving device exceeds a certain amount, the reception buffer 50
It is necessary to tell the transmitting device to temporarily stop transmitting data in order to prevent 5 from overflowing. When the amount of data stored in the reception buffer 505 becomes smaller than another certain amount as a result, it is necessary to notify the transmitting device to restart data transmission. Therefore, the flow control means 50
6 is transmitted to the isochronous transfer buffer 504 as a flow control command under the control of the host controller 501.

By using such a configuration, data flow control can be performed by isochronous transfer.

(Fourth Embodiment) FIG. 6 is a diagram showing a data transmission apparatus according to a fourth embodiment of the present invention. In FIG. 6, reference numeral 601 denotes a data transfer band calculating unit, 602 denotes a flow control band calculating unit, and 603 denotes a whole required band calculating unit.

These can be configured inside the host controller in FIG. 5 of the third embodiment.

The band required for isochronous transfer of data obtained by the data transfer band calculating means 601 and the band required for isochronous transfer of flow control obtained by the flow control band calculating means 602 are the total required band calculating means. A command for requesting a required band as a whole is added by 603 and sent to a node that manages the band through a transmission path. As a result, if a necessary band is secured as a whole, the respective bands are allocated between the transmitting and receiving devices for data transfer and flow control, and data transfer is started.

[0039]

According to the invention in which one channel of the isochronous transfer is secured also for the flow control of the data transfer, there is no uncertain delay which may occur when the flow control is executed by the asynchronous transfer of the command. ,
A command for flow control can be transmitted at a certain timing.

According to the invention, the band used for the corresponding data transfer and the flow control is secured together, and an area for specifying the set of the data transfer and the flow control corresponding to the header of each packet is provided. And the flow control can be managed in association with each other by the channel and the node ID. Even when an instruction to switch the data transfer direction is issued between the devices performing the data transfer, the device has been used up to that time. By simply replacing the value of the field indicating the transmitting node of each packet with that of each other (when using a method using an area indicating the receiving node, the area is also replaced), the bandwidth is newly secured. There is no need to reliably execute data transfer and flow control in a new direction.

[Brief description of the drawings]

FIG. 1 is a diagram showing that data transfer and flow control are both performed using isochronous packets in a first embodiment of the present invention.

FIG. 2 is a diagram showing securing of a band for data transfer and flow control for isochronous transfer in the second embodiment of the present invention.

FIG. 3 is a diagram showing a method of configuring a CIP header in a second embodiment of the present invention.

FIG. 4 is a diagram showing flow control using a conventional asynchronous packet.

FIG. 5 is a diagram showing a configuration of a data transmission device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a data transmission device according to a fourth embodiment of the present invention.

[Explanation of symbols]

101, 106, 201, 206, 401, 405 cycle start packet 102, 103, 107, 108, 202, 203, 2
07, 402, 406 Isochronous packet 104, 204, 403, 407 Asynchronous packet 105, 205, 404, 408 Response to asynchronous transfer 301 ID of transmission node 302 Size of data packet 303 Number of divisions when packetizing data 304 Size of dummy data added to data when packetizing data 305 Flag indicating presence or absence of packet header 306 Extended area for future use 307 Packet counter 308 Data format 309 Flag for distinguishing data and flow control 310 Corresponding data transfer And a set number for specifying a flow control 311 An area indicating necessary information for each data format 501 Host controller 502 Host interface 503 Asynchronous transfer Use buffer 504 isochronous transfer buffer 505 receive buffer 506 flow control means 507 transmitter 508 receiver 509 Physical interface 510 the physical layer 511 cable 601 data transfer bandwidth calculation means 602 flow control bandwidth calculation means 603 total necessary bandwidth calculation means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidetoshi Takeda 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] Claims: 1. A data transmission device which receives data when transferring data between a plurality of data transmission devices transmitting and receiving data by a transmission method in which a band is secured in advance and a transmission delay is guaranteed. A data transmission that secures a band of isochronous transfer different from a band for transmission data of isochronous transfer as a transmission path of flow control for controlling a data transmission amount of the data transmission device that transmits data according to Method. 2. The data transmission method according to claim 1, wherein a total bandwidth of a bandwidth required for data transfer and a bandwidth required for flow control of the data transfer is secured at the start of the data transfer. . 3. A data transmission format having an area that can be distinguished between transmission data and flow control data in a flow that is isochronously transferred by the data transmission method according to claim 1. 4. In a flow in which isochronous transfer is performed by the data transmission method according to claim 1, transmission data and flow control data corresponding to the transmission data are different from the transmission data and the flow control data. A data transmission format having an area that can be distinguished from a flow in the transmission data and the flow control data. 5. The data transmission format according to claim 4, wherein the transmission data and the flow control data corresponding to the transmission data have areas indicating the same set number. 6. The transmission data includes an area for specifying a channel of flow control data corresponding to the transmission data, and the flow control data includes an area for specifying a channel of the flow control data corresponding to the flow control data. 5. The data transmission format according to claim 4, wherein the data transmission format has an area for specifying the channel. 7. The data transmission format according to claim 4, wherein the transmission data and the flow control data corresponding to the transmission data have an area indicating a device flowing out of the flow and a device flowing in the flow. 8. A flow which is isochronous-transferred by the data transmission method according to claim 1 and has an area for distinguishing a type of transmission data (corresponding transmission data in the case of flow control data). A data transmission format having an area for distinguishing between transmission data and flow control data. 9. An area in which transmission data and flow control data corresponding to the transmission data can be distinguished from different flows of the transmission data and the flow control data is defined as an area where the transmission data and the flow control data are different. 9. The data transmission format according to claim 8, which is included in data. 10. The data transmission format according to claim 9, wherein the transmission data and the flow control data corresponding to the transmission data have areas indicating the same set number. 11. The transmission data has an area for specifying a channel of flow control data corresponding to the transmission data, and the flow control data includes an area for specifying a channel of the flow control data corresponding to the flow control data. 10. The data transmission format according to claim 9, wherein the data transmission format has an area for specifying a channel. 12. The data transmission format according to claim 9, wherein the transmission data and the flow control data corresponding to the transmission data have an area indicating a device flowing out of the flow and a device flowing in the flow. 13. A data transmission device capable of transmitting and receiving data, comprising: a data receiving means for receiving data; a receiving buffer for storing data received by the data receiving means; and a data buffer stored in the receiving buffer. Flow control means for transmitting information for controlling the transmission of data in response thereto, overall control means for transmitting a flow control instruction to an isochronous transfer buffer based on the information of the flow control means, and isochronous transfer by the overall control means. A data transmission unit for transmitting an instruction stored in a buffer for transmission onto a transmission path. 14. The data transmission device according to claim 13, wherein said overall control means is required for data transfer bandwidth calculation means, flow control bandwidth calculation means, and data transfer obtained by said data transfer bandwidth calculation means. Bandwidth and
A data transmission apparatus comprising: an overall required bandwidth calculation unit that adds a bandwidth required for flow control obtained by the flow control bandwidth calculation unit.