JPH10285196A - Data transmission device, data reception device, data transmission method, and data transmission system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To eliminate data loss that occurs when performing flow control by changing the connection state between data transmission devices. SOLUTION: A flow control bit is set in an output plug control register oPCR in a data transmitting device as information for distinguishing whether the contents of a transmission packet are data or empty. The data receiving device checks the buffer amount for storing the received data, determines that the data transmission is stopped when the amount exceeds a certain amount, and determines that the data transmission is executed when the amount is less than the certain amount,
Based on the determination result, the flow control bit of the output plug control register oPCR of the data transmission device is set to a predetermined value, and switching between data packet transmission and empty packet transmission is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data transmission device,
The present invention relates to a data receiving apparatus, a data transmission method, and a data transmission system, and particularly relates to a digital AV (Audio Visual) device and a computer device when connected by a digital interface having an isochronous transfer function such as an IEEE 1394 interface. The present invention relates to an improved protocol for data transmission between devices.

[0002]

2. Description of the Related Art Among digital interfaces for connecting digital AV equipment (hereinafter referred to as AV equipment) and computer equipment, an IEEE 1394 interface has an isochronous (synchronous) transfer mode for real-time data transfer and an asynchronous (synchronous) transfer mode. This is a serial interface having both transfer modes (asynchronous). Asynchronous transfer occurs at any time.
While isochronous transfer is used to transfer data at regular intervals, whereas isochronous transfer is used to transfer multimedia data such as video and audio, it is suitable for real-time transfer. A transfer speed is secured for media data transfer, and data transfer with a guaranteed transmission delay is enabled. This real-time transmission by isochronous transfer transfers packetized data at a cycle of 8 kHz, that is, every 125 μs.

The IEEE 1394 interface is defined by three layers as shown in FIG. The three layers are a physical layer PL that performs a physical interface between a bus and an electric signal, and the like.
A link layer LL for transmitting and receiving packets and a transaction layer TL for performing processing related to asynchronous data.

[0004] In the physical layer PL, I
F is an interface unit for interfacing with a medium (bus), AB is an arbitration unit for arbitrating the bus, and ED is an encoding and decoding unit for encoding and decoding signals. In the link layer LL, PR is a packet receiving unit that performs packet reception, PS is a packet transmitting unit that performs packet transmission, and CC is a cycle control unit that performs transmission and reception cycle control. Further, on the side of the transaction layer TL, BM is a bus management controller for managing and controlling the bus, NC is a node controller for controlling the nodes,
RM is an isochronous resource management unit that manages isochronous resources, and BMG is a bus manager that manages buses. For example, IEC1883 is a standard for flowing audio and video data over the IEEE1394 interface, which is also called an AV protocol.

FIG. 7 shows a packet format of the AV protocol.
2 is a CRC (Cycric Redu) for the packet header 701.
ndancy check), 703 is a CIP header, 704 is data, and 705 is a CRC for the data 704. Among these, packet header 701, header CRC
702, data 704, and data CRC 705 are IEEE
It is a format of a data packet for isochronous transfer flowing on the 1394 interface, and the AV protocol has a CIP header 703 added thereto.

The CIP header 703 is obtained by adding information and a header specific to an AV signal to the head of the data field. In the CIP header 703, SID is the node ID of the transmitting node, DBS is a packetization unit, and FN is Number before division, QPC is the number of quadlets added for division, SPH is a flag in the source packet header, DBC is a counter for detecting packet loss, FMT is a signal format ID, and 50/60 is a signal format ID. 1
The number of fields per second and TYPE indicate information indicating whether the video format corresponds to SD or HD, respectively.

In the IEC1883, the connection between the transmitting device and the receiving device for exchanging data by isochronous transfer is managed by the concept of a virtual plug assigned to each device. This is a plug control register (PCR). It is assumed that a plurality of plugs can exist in each device, and data is input and output through the plugs.

[0008] Data transmitted from one device by isochronous transfer passes through an isochronous channel on a bus through an output plug of the device, and is transferred to another device through an input plug on a receiving side. You. Output plug control registers (oPCR) and output master plug registers (oMPR) manage output plugs, and input plug control registers (iPCR) and input master plug registers (iMPR) manage input plugs. ). The output master plug register and input master plug register control attributes common to all isochronous transfer data output or input by the corresponding device.The output plug control register and input plug control register , For controlling the attribute of each isochronous transfer data.

As a connection mode for transferring data between data transmission devices such as a computer and an AV device, a point-to-point connection (point-to-point connection) that connects one input plug of one device to one output plug of another device is provided. -to-point connection) and one of the devices
There is a broadcast connection that connects one input plug or output plug to a channel on the bus. The broadcast connection is used when one device simultaneously exchanges data with a plurality of devices.

Next, FIG. 8 shows an image of a state in which two AV devices are connected to each other with a plug, for example, when the two AV devices are connected to an IEEE1394 interface. Note that the plug is a concept as described above and does not physically exist but represents a virtual input / output point when each device inputs and outputs data.

In FIG. 8, reference numeral 801 denotes IEEE 1394.
802 represents a channel on which isochronous transfer is performed. Reference numerals 803, 808, and 809 denote input plug control registers. It is assumed that an input plug for data input virtually exists here.
Input master plug registers 804 and 810 manage attributes common to the input plug control registers for each device. Reference numeral 805 denotes an output plug control register. It is assumed that an output plug for data output virtually exists here. 8
An output master plug register 06 manages attributes common to the output plug control registers for each device. The numbers [0] and [1] assigned to the input plug control register and the output plug control register are used to distinguish the individual registers. Reference numerals 807 and 811 denote AV devices as an example of a device having the IEEE 1394 interface.

The arrangement of these plug control registers in FIG. 8 is an example. As shown in FIG. 8, the devices having the IEEE1394 interface are both AV devices, and one of the two AV devices is dedicated to input. The arrangement is not limited to the arrangement in which the other terminal is used for both input and output.

FIG. 9 shows a state of packet transfer in the IEEE 1394 interface. In FIG. 9, CYS denotes a packet indicating a cycle start, C
H1, CH2,..., CHn are isochronous packets transmitted by isochronous transmission,
This shows packets corresponding to channels 2,..., Channel n. PA and PB are asynchronous packets that are added only when data to be transferred asynchronously is generated, and indicate packets corresponding to the packets a and b. ACK is an acknowledgment for confirming the delivery of these asynchronous packets.

Next, the operation of FIG. 8 will be described. The multimedia data generated by the transmitting AV device 807 is
The data packet becomes a data packet as shown in FIG. 9 and is transmitted via an output plug virtually existing in the output plug control register 805 to the IEEE 1394 bus 80.
One isochronous channel 802 is transmitted. Although the data packet on the isochronous channel 802 reaches all the devices connected to the IEEE 1394 bus 801, the device to be received is specified by the header included in the data packet. In the example of FIG. The receiving AV device 811 receives the data via an input plug virtually existing in the input plug control register 808. Next, in FIG.
2 shows an actual internal configuration of an interface portion in a data transmission device having an IEEE1394 interface, such as a computer or an AV device. In FIG. 10, reference numeral 1001 denotes an IE provided in a certain data transmission device.
A host controller device that controls the entire IEEE 1394 interface, and performs a function corresponding to a transaction layer that manages read and write transactions actually performed by the IEEE 1394 interface.

Reference numeral 1000 denotes the host controller device 100
By reading / writing the internal register,
This is a link layer device that performs data transfer based on the EEE1394 standard. This corresponds to a link layer of the IEEE 1394 interface, and includes a host interface 1002, a buffer unit 1000a, a transmitting / receiving unit 1000b, a register 1011 and a controller unit 1.
012 and is realized by, for example, one IC chip. 1002 is a host controller device 1001
It is a host interface for exchanging commands with the host. Reference numeral 1000a denotes a buffer unit for storing data, which includes an asynchronous transfer buffer 1003, an isochronous transfer buffer 1004, and a reception buffer 1005.
It is composed of The asynchronous transfer buffer 1003 stores data for asynchronous transfer, the isochronous transfer buffer 1004 stores data for isochronous transfer, and the reception buffer 1005 stores received data.

A transmission / reception unit 1000b for transmitting / receiving data includes a transmitter 1006 and a receiver 1006.
7, a physical interface 1008. The transmitter 1006 transmits the data stored in the transmission data buffer 1003 or 1004 to the physical interface 1008.
The receiver 1007 is a physical interface 100
The physical interface 1008 exchanges data with the physical layer device 1009. Reference numeral 1011 denotes a register, which includes the plug control register and the master plug register shown in FIG. Reference numeral 1012 denotes a controller which controls the entire link layer apparatus 1000 in accordance with the contents of the register 1011.

Reference numeral 1010 denotes a cable for connecting to an IEEE 1394 interface of another device, and the IEEE 1394 bus in FIG. 8 corresponds to this cable. Reference numeral 1009 denotes a physical layer device for connecting the cable 1010 and the link layer device 1000, which is an IEEE 139.
It corresponds to a physical layer of four interfaces, and is realized by, for example, one IC chip.

FIG. 11 shows the physical layer device 1 of FIG.
This indicates the format of the signal at the physical level, which is sent to the IEEE1394 cable according to 009. The signal at this physical level is a set of a data signal and a strobe signal which are transmitted to an IEEE 1394 cable, and the strobe signal is obtained by taking the exclusive OR of the data signal and the strobe signal. The clock signal is generated so that it can be reproduced.

Next, the operation inside the IEEE 1394 interface shown in FIG. 10 will be described. The host controller 1001 transmits data generated by a data transmission device such as an AV device to the link layer device 1000 via the host interface 1002. The link layer apparatus 1000 is provided with both an asynchronous transfer buffer 1003 and an isochronous transfer buffer 1004 according to the nature of the data to be transmitted. Transfer buffer 10 according to
03 and the buffer 1004 for isochronous transfer. Next, the data stored in the asynchronous transfer buffer 1003 or the isochronous transfer buffer 1004 is transmitted by the transmitter 1006 to the physical layer device 1009 via the physical interface 1008. Chronos transfer is executed with priority. In the physical layer device 1009, these data are actually stored in the cable 1010 as shown in FIG.
Is converted to a signal format to be put on the
Send out to 394 interface.

Conversely, data transmitted from the IEEE 1394 interface of another device is transmitted to the physical layer device 1009 via the cable 1010, and the link layer device 1 is transmitted by the physical layer device 1009.
000, and is taken into the link layer apparatus 1000 by the physical interface 1008. This data is received by the receiver 1007, stored in the reception buffer 1005, transmitted to the host controller 1001 of the device via the host interface 1002, and sent to another portion inside the device.

The register 1011 in FIG. 10, that is, the register such as the output plug control register in FIG. 8, is used for controlling the above-described transmission / reception operation by referring to its contents by the controller section in FIG. However, it is also used for the following flow control.

That is, in FIG. 10, when the data stored in the reception buffer 1005 of the receiving device exceeds a certain amount, the transmitting device temporarily stops data transmission in order to prevent the receiving buffer 1005 from overflowing. I need to tell. As a result, the reception buffer 1005
When the data stored in the storage device becomes smaller than a certain fixed amount different from the certain fixed amount, that is, when the data becomes further smaller than another certain fixed amount equal to or smaller than the certain fixed amount, transmission of data to the transmitting device is restarted. Need to tell.

FIG. 12 shows a format of data to be written in a conventional output plug control register, which is also used for such a flow control. In FIG. 12, reference numeral 1201 denotes an online flag area, which indicates whether the corresponding output plug is online.
This indicates whether the connection is offline, that is, whether the connection is on or off. Reference numeral 1202 denotes a broadcast connection counter area, which indicates whether or not there is a broadcast connection that can be transmitted to all devices connected to the IEEE 1394 bus. Reference numeral 1203 denotes a point-to-point connection counter area, which indicates the number of point-to-point connections existing in one output plug. Reference numeral 1204 denotes a spare area for future function expansion, and its role is not defined at present. Reference numeral 1205 denotes a channel number area indicating a channel number on the bus used when the output plug transfers isochronous data. Reference numeral 1206 denotes a data rate area indicating a data transfer speed, 1207 denotes an overhead ID area indicating the amount of overhead added to data at the time of isochronous transfer, and 1208 denotes a payload area, which is pure data transferred every cycle. It indicates the amount.

FIG. 13 shows a format of data to be written into a conventional input plug control register. In FIG. 13, reference numeral 1301 denotes an online flag area, which indicates whether the corresponding input plug is online or offline, that is, whether the connection is on or off. Reference numeral 1302 denotes a broadcast connection counter area.
Indicates whether there is a broadcast connection that can be transmitted to all devices connected to the 94 bus. Reference numeral 1303 denotes a point-to-point connection counter area, which indicates the number of point-to-point connections existing in one input plug. Reference numeral 1304 denotes a spare area for future function expansion, and its role is not defined at present. Reference numeral 1305 denotes a channel number area indicating a channel number on a bus used when the input plug transfers isochronous data, and reference numeral 1306 denotes a spare area for future function expansion.

The contents of such a plug control register can be changed by the device owning the register itself, but can also be changed by an external device using a lock transaction through the IEEE 1394 interface. Note that a lock transaction is a process in which data is transferred from a request side to a response side, data is processed at a specific address on the response side, and sent back to the request side. The asynchronous packet PA or the like prepared separately for isochronous data as shown in FIG.

Next, each of the above operations will be described together with the operation at the time of flow control. As described above, in FIG. 8, the multimedia data generated by the transmission-side AV device 807 becomes a data packet as shown in FIG. 9 and is transmitted via an output plug virtually existing in the output plug control register 805. IEEE 1394
It is sent to the isochronous channel 802 of the bus 801. The data packet on the isochronous channel 802 reaches all the devices connected to the IEEE 1394 bus 801, and the device to be received is specified by the header included in the data packet. The receiving AV device 811 receives the input plug virtually in the input plug control register 808.

[0027] As shown in FIG.
In step 1401, the controller unit 1012 of the receiving AV device 811 that has received the data from the receiving AV device 7 receives the data from the receiving buffer 10 of the receiving AV device 811 shown in FIG.
In step 1402a, the host controller device 1001 of the receiving AV device transmits the data of the transmitting AV device when the data amount of the receiving buffer 1005 exceeds a certain amount. It is determined to stop, and in step 1402b, when the amount of data in the reception buffer 1005 is equal to or smaller than another certain amount, it is determined to execute data transmission of the transmission-side AV device. If it is determined that the transmission of data from the transmitting AV device is to be stopped, step 1403
In a, the host controller device 1001 of the receiving AV device issues a command requesting to stop data transmission, and if it is determined to execute data transmission of the transmitting AV device, in step 1403b, The host controller 1001 of the AV device issues a command requesting the start of data transmission.

A command for requesting execution or stop of data transmission, which is determined and issued by the host controller device 1001 of the receiving AV device, is based on IEEE.
By the lock transaction of the 1394 interface, the asynchronous packet P as shown in FIG.
A, PB, etc., are transferred to the transmitting AV equipment 807,
The content of the online flag of the output plug control register 805 of the transmitting AV device is directly rewritten. Also, the host controller device 1 of the receiving AV device
The request command, such as execution or stop of data transmission, which is determined and issued according to 001, is transmitted to the input plug control register 80 of the receiving AV device.
8 is directly rewritten.

That is, for example, when the buffer amount of the receiving device becomes equal to or more than a certain value and the data transmission is stopped, in step 1404a, the transmitting side sets the online flag 1201 of the output plug control register 805 shown in FIG. 0 ”, and the online flag 130 of the input plug control register 808 shown in FIG.
1 is set to “0”. On the other hand, when executing data transmission, in step 1404b, the transmission side sets the online flag 1201 of the output plug control register 805 shown in FIG. FIG.
The online flag 1301 of the input plug control register 808 shown in FIG.

The controller 1 of the transmitting AV device 807
012 is transmitting data while referring to the output plug control register. Therefore, as shown in step 1405a, from the moment when the online control bit 1201 of the output plug control register is turned off, that is, "0". Stop sending data.

The controller unit 1012 of the receiving AV device 811 transmits the on-line control bit of the input plug control register 808 when, for example, the data transmission is stopped by the above-mentioned request command such as the execution or the stop of the data transmission. 1301 is rewritten to “0”. Next, the online control bit of the input plug control register 808 is set to “0”.
It stops receiving data from the moment it becomes.

On the other hand, as shown in step 1405b, the controller unit 1012 of the transmission-side AV device 807 transmits data from the moment when the online control bit 1201 of the output plug control register 805 is turned on, ie, "1". Start.

When data transmission is started, the controller unit 1012 of the receiving AV device 811 rewrites the online control bit 1301 of the input plug control register 808 to “1”. Next, data reception starts at the moment when the online control bit 1301 of the input plug control register 808 becomes "1".

FIGS. 15 and 16 show what control is performed by the controller of the link layer device by setting data in the online flag of the plug control register, that is, the online control bit.

Next, the operation of the controller will be described. In the receiving AV device, step 150 in FIG.
In FIG. 10, the controller unit 1012 in FIG. 10 observes the contents of the register 1011. In step 1502, it is determined whether the contents of the online flag 1301 located at the most significant bit of the register 1011 is "0" or "1". .

Next, when the content of the online flag 1301 becomes “0”, the controller 1012 determines in step 1503 that the receiver 1
If the data reception operation is stopped at 007, and the content of the online flag 1301 becomes "1",
In 04, the receiver 1007 starts data reception operation.

In the transmission side AV device, in step 1601 of FIG. 16, the controller 101 of FIG.
2 observes the contents of the register 1011, and in step 1602, determines whether the contents of the online flag 1201 located at the most significant bit of the register 1011 is “0” or “1”.

Next, when the content of the online flag 1201 becomes "0", the controller unit 1012 stops the data transmission operation to the transmitter 1006 of the transmission / reception unit 1000b in step 1603, and the content of the online flag 1201 becomes "0". If it becomes 1 ", in step 1604, the transmitter 1006 starts the data transmission operation.

The conventional data transfer system is configured as described above. In addition to the asynchronous (asynchronous) transfer mode for normal data transmission, the isochronous transfer for guaranteeing an optimum transfer band for multimedia data transfer. A mode is provided, whereby images and sounds being transmitted can be transferred without interruption.

Further, since the bus is a high-speed serial bus and the connection method thereof is versatile and can be connected by daisy chain connection or node branch connection, for example, as shown in FIG. Workstation 1701, CD-ROM drive 1702, camera 1
Various devices such as a PC 703, a personal computer (PC) 1704, a hard disk drive (HDD) 1705, a printer 1706, and a scanner 1707 can be connected in a highly flexible connection mode.

Then, among various devices (nodes) connected to the network constituted by the serial bus in this way, the IEEE 13 of the device whose activation is the slowest is described.
The 94 interface automatically becomes the parent node, and the IEEE 1394 of all devices connected to the network
The connection configuration is recognized and managed for the interface. Therefore, so-called plug and play, in which various devices are added to or removed from the network using the IEEE 1394 interface while the power is on, is possible.

As shown in FIG. 18, when various peripheral devices are connected to one device such as a personal computer, for example, an I / O port 1802 for SCSI, an I / O port for outputting video signals, or the like. Port 1803, audio signal output I / O port 1804, serial I / O port 180
5. Port 1806 for power supply, I / O for keyboard
It is common to provide different I / O ports for each device, such as an O port 1807 and a parallel I / O port 1808, to connect various devices. By adopting the IEEE 1394 interface, one device can be used. IEEE
The I / O port 1801 for E1394 makes it possible to perform input and output in a unified manner, and it is possible to greatly improve the installation space and the installation cost of the I / O port.

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

Therefore, in order to prevent the receiving device from becoming unable to receive data, it is necessary to perform a so-called flow control for controlling data transfer from the receiving device to the transmitting device. As one of the methods for realizing this flow control, as described above, the online flags 1201 and 1301 are set by using the output plug control register and the input plug control register.
There is a method of making the connection between devices online or offline by switching 1.

[0045]

However, according to this conventional protocol, when the receiving device issues a command requesting to stop data transmission, the transmitting device rewrites the online flag of the output control register, The receiving side rewrites the online flag of the input control register, but at this time, the transmitting side must transmit a lock transaction packet by transmitting a lock transaction packet, so the transmitting side and the receiving side are not necessarily synchronized. Therefore, the rewriting may not be performed, and the rewriting may be performed later on the transmission side than on the reception side.

That is, the transmission side stops data transmission at the moment when the online bit of the output control register becomes "0", and the reception side starts data transmission at the moment when the online bit of the input control register becomes "0". If the receiving side goes offline due to delay in rewriting of the transmitting side, the data arriving at the interface after switching from online to offline will be discarded while remaining on the bus,
Also, no packets will be sent while offline,
It falls into the situation.

More specifically, since no data can be received during offline, even if data remaining on the bus arrives at the receiving device when switching from online to offline. However, there is a problem in that the arriving data is discarded, and data may be missed in the receiving device.

The present invention has been made in view of the above-mentioned problems of the prior art. When a data receiving side intends to perform flow control, the flow control can be performed by an easy method without causing data loss. It is intended to provide a data transmission device, a data reception device, a data transmission method, and a data transmission system that can be executed.

[0049]

According to a first aspect of the present invention, there is provided a data transmitting apparatus for outputting data on a data transmission path, the data being transmitted when the data is transmitted in packet units. Data transmission control information storage means for storing control information for controlling whether to send a packet or to send an empty packet; and a packet carrying the data based on the data transmission control information in the data transmission control information storage means. And a data transmitting means for transmitting data by outputting one of the empty packets.

According to a second aspect of the present invention, in the data transmission apparatus according to the first aspect, the data transmission control information storage means includes a register provided in the data transmission apparatus; The register has a specific n bits (n is an integer of 1 or more) for distinguishing whether to send a packet carrying data or an empty packet.
Are provided.

According to a third aspect of the present invention, in the data receiving apparatus for inputting data from a data transmission path, a buffer for temporarily storing the received data when receiving the data in packet units. A data reception determining unit for determining whether to continue receiving data according to an amount of data stored in the buffer; and transmitting a packet carrying the data to a data transmission device according to a result of the data reception determining unit. And a data transmission control request means for instructing whether to transmit an empty packet.

According to a fourth aspect of the present invention, in the data receiving apparatus according to the third aspect, a data transmission control command sent from the data transmission control request means to the data transmitting apparatus carries data. Command to send an empty packet or an instruction to send an empty packet.
This is performed by using a specific n-bit (n is an integer of 1 or more) flag of a data string of a packet constituting the data transmission control instruction.

Further, according to the data transmission method of the present invention, a data transmission apparatus for transmitting data in packet units and a data receiving apparatus for receiving data from the data transmission apparatus in packet units are provided. In the data transmission method described above, the data receiving device issues a data transmission control command for instructing whether to send a packet carrying data or to send an empty packet, and the data transmitting device is based on the data transmission control command, The data transmission control information storing means rewrites the data transmission control information for discriminating whether to send a packet carrying data or to send an empty packet.
One of a packet carrying data and an empty packet is sent while referring to the data transmission control information.

In the data transmission system according to the sixth aspect of the present invention, when transmitting data in packet units, control information for controlling whether to transmit a packet carrying data or an empty packet is transmitted. Data transmission control information storage means to be stored, and data transmission is performed by outputting either a packet carrying the data or an empty packet based on the data transmission control information in the data transmission control information storage means. A data transmission device having data transmission means, a buffer for temporarily storing received data when receiving data in packet units, and determining whether to continue receiving data according to an amount of data stored in the buffer. A data reception determining means for transmitting a packet carrying data to the data transmitting apparatus according to a result of the data reception determining means. And a data transmission control request means for instructing whether to send an empty packet or to send an empty packet, wherein the data receiving device sends data carrying a packet or an empty packet. The data transmission device issues a transmission control command, and the data transmission device, based on the data transmission control command, discriminates whether to send a packet carrying data or an empty packet stored in the data transmission control information storage means. In addition to rewriting the information, the data transmitting apparatus transmits either a packet carrying data or an empty packet with reference to the data transmission control information every time a packet is transmitted.

[0055]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. In the first embodiment of the present invention, even when data transmission should be stopped by flow control, the online state between the transmitting and receiving devices is maintained, and an empty packet is used instead of a data packet on the transmitting side. By sending
This is to prevent the receiving side from missing data.

Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a data transmission system according to a first embodiment of the present invention, and shows an image of connection using a plug, taking as an example a case where two AV devices are connected to an IEEE1394 interface.

In FIG. 1, reference numeral 101 denotes IEEE1394.
, And 102 indicates a channel on which isochronous transfer is performed. Reference numerals 103, 108, and 109 denote input plug control registers. It is assumed that an input plug for data input virtually exists here.
Input master plug registers 104 and 110 manage attributes common to the input plug control registers for each device. Reference numeral 105 denotes an output plug control register. It is assumed that there is an output plug for data output virtually here. 106
Is an output master plug register, which manages attributes common to the output plug control registers for each device. The numbers [0] and [1] assigned to the input plug control register and the output plug control register are used to distinguish the individual registers. Also, 107 and 111 are IEEE
An AV device is shown as an example of a device connected to the E1394 interface.

The arrangement of these plug control registers in FIG. 1 is merely an example. As shown in FIG. 1, the devices connected to the IEEE 1394 interface are both AV devices, and one of the two AV devices is one. It is not limited to an arrangement in which only input is used and the other is used for both input and output.

Next, the operation of FIG. 1 will be described. The multimedia data generated by the transmitting AV device 107 is
The data packet becomes a data packet as shown in FIG. 9 and is transmitted to the IEEE 1394 bus 10 via an output plug virtually existing in the output plug control register 105.
The signal is transmitted to one isochronous channel 102. A data packet on the isochronous channel 102 reaches all devices connected to the IEEE 1394 bus 101, but a device to be received is specified by a header included in the data packet. In the example of FIG. It is received by the receiving AV device 111 via an input plug virtually existing in the input plug control register 108.

As shown in FIG. 1, only the block configuration is shown, so that the configuration and operation are the same as those of the conventional configuration shown in FIG. The format of the data written in the output plug control register is different from the conventional one.

FIG. 2 is a diagram showing the actual internal configuration of the IEEE 1394 interface of each device. In FIG. 2, reference numeral 201 denotes an IE provided in a certain data transmission device.
A host controller device that controls the entire IEEE 1394 interface, and performs a function corresponding to a transaction layer that manages read and write transactions actually performed by the IEEE 1394 interface.

Reference numeral 200 denotes that the host controller 201 reads / writes an internal register, so that the
It is a link layer device that performs data transfer based on the E1394 standard. This corresponds to the link layer of the IEEE 1394 interface, and includes the host interface 202, the buffer unit 200a, and the transmission / reception unit 20.
0b, a register 211, and a controller unit 212, for example, one IC chip. 202
Is a host interface for exchanging commands with the host controller device. Reference numeral 200a denotes a buffer unit for storing data, which comprises an asynchronous transfer buffer 203, an isochronous transfer buffer 204, and a reception buffer 205. The asynchronous transfer buffer 203 stores data for performing asynchronous transfer, and the isochronous transfer buffer 204 stores data for performing isochronous transfer.
Reference numeral 5 stores received data.

A transmission / reception unit 200b for transmitting / receiving data includes a transmitter 206, a receiver 207, and a physical interface 208. The transmitter 206 includes a transmission data buffer 203 or 20.
Data stored in the physical interface 2
08, the receiver 207 sends data received from the physical interface 208 to the reception buffer 205, and the physical interface 208 exchanges data with the physical layer device 209. A register 211 includes the plug control register and the master plug register shown in FIG. A controller unit 212 controls the entire link layer device 200 according to the contents of the register 211.

Reference numeral 210 denotes a cable for connecting to the IEEE 1394 interface of another device,
The EEE1394 bus corresponds to this. A physical layer device 209 connects the cable 210 and the link layer device 200. The physical layer device 209 corresponds to a physical layer of an IEEE 1394 interface, and is realized by, for example, one IC chip.

Next, the operation inside the IEEE 1394 interface of FIG. 2 will be described. The host controller 201 transmits data generated by a data transmission device such as an AV device to the link layer device 200 via the host interface 202. The link layer device 200 has an asynchronous transfer buffer 203 and an isochronous transfer buffer 20 according to the nature of data to be transmitted.
4 are prepared, and the host controller device 2
The data to be transmitted under the control of 01 is stored in either the asynchronous transfer buffer 203 or the isochronous transfer buffer 204 according to the type. Next, the data stored in the asynchronous transfer buffer 203 or the isochronous transfer buffer 204 is transmitted to the physical interface 20 by the transmitter 206.
The transmission is performed to the physical layer device 209 via the P.8, and at this time, the isochronous transfer is executed with priority over the asynchronous transfer. Physical layer device 2
In step 09, the data is converted into a signal format that can be actually put on the cable 210 as shown in FIG. 11, and sent out to the IEEE 1394 interface of the other device.

Conversely, data transmitted from the IEEE 1394 interface of another device is transmitted to the physical layer device 209 via the cable 210, converted by the physical layer device 209 into an internal signal format of the link layer device 200, and The data is taken into the link layer device 200 by 208. This data is received by the receiver 207, stored in the reception buffer 205, transmitted to the host controller 201 of the device via the host interface 202, and sent to another portion inside the device.

As described above, since FIG. 2 shows only a block configuration, the configuration and operation are the same as those of the conventional FIG. 10, but in the first embodiment, As described above, the format of the data written in the register is different from the conventional one, and the control operation of the controller unit defined by the new data format is different from the conventional one.

FIG. 3 is a diagram showing a format of data to be written in the output plug control register of the data transmission device according to the first embodiment of the present invention. In FIG. 3, reference numeral 301 denotes an online flag area, which indicates whether the corresponding output plug is online or offline, that is, whether the connection is on or off. Reference numeral 302 denotes a broadcast connection counter area, which indicates whether or not there is a broadcast connection that can be transmitted to all devices connected to the IEEE 1394 bus. Reference numeral 303 denotes a point-to-point connection counter area, which indicates the number of point-to-point connections existing in one output plug. 3
Reference numeral 04 denotes a flow control area for controlling data transfer, and its value is, for example, "1" when stopping data transmission, and "0" when executing data transmission.

In the case of the first embodiment, what is stopped by the flag in the flow control area, that is, the flow control bit, is the transmission of the data itself, and does not disconnect the connection or change the state of the plug. . Therefore, even while the data transfer is stopped by the flow control bit, the online state is maintained, and the transmission of empty packets continues.

Reference numeral 305 denotes a spare area for future function expansion, and its role is not defined at present. Reference numeral 306 denotes a channel number area indicating a channel number on the bus used when the output plug performs isochronous data transfer. Reference numeral 307 denotes a data transfer speed region indicating the data transfer speed, and reference numeral 308 denotes an overhead ID region indicating the amount of overhead added to the data when performing the isochronous data transfer. 30
Reference numeral 9 denotes a payload area, which indicates a pure data amount to be transferred every cycle.

In the first embodiment, since the data receiving side only needs to maintain the online state regardless of the data transmission state and the data stop state as described above, the receiving side is different from the transmitting side. The format of the data to be written to the input plug control register is the same as that of the conventional one shown in FIG. 13, and its online flag is set to "1" regardless of whether the data is in the transmission state or the stop state. You should keep it.

By the way, the register shown in FIG.
The output plug control register and the like are used for the above-described transmission / reception operation control by referring to the contents by the controller unit in FIG. 2, but are also used for the following flow control. .

That is, when the data stored in the receiving buffer 205 of FIG.
In order to prevent the receiving buffer 205 from overflowing, it is necessary to inform the transmitting device to temporarily stop transmitting data. As a result, when the data stored in the reception buffer 205 becomes smaller than another certain amount, that is, when the data becomes further smaller than another certain amount equal to or less than the certain amount, transmission of data to the transmitting device is restarted. Need to be told.

Further, referring to FIG. 4, the controller 212 of the receiving AV device 111 that has received the data from the transmitting AV device 107 stores the data in the receiving buffer 205 of the receiving AV device in step 401. When the amount of data in the reception buffer 205 exceeds a certain amount by knowing the amount of data, in step 402a, the host controller 20
1 determines to stop data transmission, step 4
In 02b, when the data amount of the reception buffer 205 is equal to or less than a certain amount, it is determined to execute data transmission.

As a result, the request to execute or stop the transmission of data determined by the host controller 201 of the receiving AV apparatus is made by the lock transaction of the IEEE 1394 interface as shown in FIG.
Are transferred to the transmission-side AV device 107 using the asynchronous packets PA, PB and the like as shown in (1), and directly rewrite the contents of the output plug control register 105 of the transmission-side AV device. That is, for example, when the data transmission is stopped, the flow control bit 304 of FIG. 3 indicating the contents of the output plug control register 105 is set to “1”, and when the data transmission is executed, the flow control bit 304 is set to “0”. Set to. Sending AV
Since the link layer device 200 of the device 107 transmits data while referring to the output plug control register in each cycle, control such as transmission and stop of data is performed from the next cycle in which the output plug control register is rewritten. Becomes possible.

That is, when the host controller 201 of the receiving AV device determines that the buffer capacity of the receiving device is equal to or more than a certain value, in step 403a, the host controller device 201 of the receiving AV device executes a read transaction to execute The contents of the output plug control register 105 are read and used as reference data. Next, in step 404a, the host controller device 201 of the receiving AV device sets the flow control bit of the read reference data of the output plug control register to "1" to create update data of the output plug control register.
Then, in step 405a, the host controller device 201 of the receiving AV device transmits reference data and update data of the output plug control register to the transmitting AV device in a lock request packet.

Further, in step 406a, the controller section 212 of the transmitting AV device compares the current contents of the output plug control register 105 with the reference data of the output plug control register received by the lock request. If the comparison shows that they do not match, step 40
In step 7a, the receiving AV device returns to step 404a using the current content of the output plug control register 105 sent by the lock response packet from the transmitting AV device as the next reference data.

If they match, in step 408a, the controller unit 2 of the transmitting AV device
12 updates the current output plug control register to the updated data of the output plug control register received by the lock request, and in step 409a, the controller 212 of the transmission side AV device updates the updated output plug control register. , The transmitter 206 controls to transmit an empty data packet, that is, a data packet having only a header.

On the other hand, in step 402a, it is determined that the receiving buffer capacity of the receiving AV device is not equal to or more than the predetermined amount.
If it is determined that the receiving buffer amount of the device is equal to or less than another certain amount, in step 403b, the host controller device 201 of the receiving AV device reads the contents of the output plug control register 105 of the transmitting AV device by a read transaction. , And this is used as reference data. Next, in step 404b, the receiving AV
The host controller 201 of the device sets the flow control bit of the read reference data of the output plug control register to “0”, and creates update data of the output plug control register.
Then, in step 405b, the host controller device 201 of the receiving AV device uses the link layer device 200 to transmit the reference data and the update data of the output plug control register to the transmitting AV device as a lock request packet.

Further, in step 406b, the controller unit 212 of the transmitting AV device compares the current contents of the output plug control register 205 with the reference data of the output plug control register received by the lock request. If the comparison shows that they do not match, step 40
In step 7b, the receiving AV device returns to step 404b using the current contents of the output plug control register 105 sent by the lock response packet from the transmitting AV device as the next reference data.

If they match, in step 408b, the controller 2 of the transmitting AV device
12 updates the current output plug control register to the updated data of the output plug control register received by the lock request. In step 409b, the controller unit 212 of the transmission-side AV device transmits the updated output plug control register. , The transmitter 206 performs control so as to transmit a packet carrying data, that is, an original data packet which is not an empty packet having only a header.

FIG. 5 shows what control is performed by the controller of the link layer apparatus by setting data in the flow control flag of the output plug control register, that is, the flow control bit.

Next, the operation of the controller will be described. In the transmission side AV device, in step 501 of FIG. 5, the controller unit 212 of FIG.
In step 502, it is determined whether the content of the flow control flag 304 located in the fourth area from the most significant bit of the register 211 is “0” or “1”.

Next, when the content of the flow control flag 304 becomes “0”, the controller 212
03, the transmitter 2 of the transmission / reception unit 1000b
In step 504, the transmitter 206 starts transmitting an empty data packet when the flow control flag 304 is set to "1".

As described above, according to the first embodiment, whether to send a data packet or an empty packet in the output plug control register of the transmitting apparatus, separately from the information indicating the connection state between the devices. By setting the information that distinguishes the packet and rewriting the information that distinguishes the contents of the packet according to the request of the receiving device, it is possible to control data transmission without changing the connection status between devices from online to offline As a result, the data arrived immediately after going offline as in the conventional flow control is not discarded, and the data is not lost.

The position of the flow control bit 304 in the data format to be written in the output plug control register of FIG. 3 is one bit of the two-bit area corresponding to the future spare area in the conventional specification of FIG. , The compatibility with the conventional specification of FIG.
Although it is possible to add a flow control function without missing data, this is not limited to the position shown in FIG. It is possible to perform Also, the flow control bit 304 is not necessarily limited to one bit, and it is possible to realize a flow control with further expanded functions by configuring the flow control bit 304 with a plurality of bits.

Further, the register for setting the flow control bit 304 is not limited to the output plug control register, but can be realized by another equivalent register. The rewriting of the output plug control register 105 of the transmitting AV device is performed by the receiving AV device.
The device requests a command, and then the sender AV
An indirect method in which the device rewrites itself is also possible. Further, in the first embodiment, the IEEE 13
Although only 94 has been described, any digital interface can be applied as long as it has the same function as that of IEEE 1394 with respect to isochronous transfer.

[0088]

As described above, according to the data transmitting apparatus according to the first aspect of the present invention, when transmitting data in packet units, the data transmitting apparatus for outputting data on the data transmission path has a Data transmission control information storage means for storing control information for controlling whether to transmit a packet carrying a packet or an empty packet; and loading the data based on the data transmission control information in the data transmission control information storage means. And data transmission means for transmitting data by outputting either a packet or an empty packet, so that data transmission is stopped without disconnecting the data receiving device. There is an effect that a data transmission device capable of performing the above can be obtained.

[0089] According to the data transmitting apparatus of the second aspect of the present invention, in the data transmitting apparatus of the first aspect, the data transmission control information storage means stores data from a register provided in the data transmitting apparatus. Since the register has a specific n-bit (n is an integer of 1 or more) flag for distinguishing whether to send a packet carrying data or to send an empty packet, By rewriting the specific n bits of, it is possible to control whether to send a packet carrying data or to send an empty packet, and to stop transmitting data without disconnecting the connection to the data receiving device. There is an effect that a possible data transmission device can be obtained.

According to the data receiving apparatus of the third aspect of the present invention, when receiving data in packet units, the received data is temporarily stored in the data receiving apparatus that inputs data from the data transmission path. A buffer, data reception determining means for determining whether or not to continue receiving data according to an amount of data stored in the buffer, and a packet having data loaded on a data transmitting device according to a result of the data reception determining means. And a data transmission control request means for instructing whether to transmit an empty packet or an empty packet, so that a transmission request is issued to the data transmission side in accordance with the amount of data stored in the buffer on the data reception side. Flow control can be performed by sending a packet carrying data or sending an empty packet to the data transmission device, There is an effect that it is possible to perform the flow control without any connection with the chromatography data transmitting apparatus to the sectional.

According to a fourth aspect of the present invention, in the data receiving apparatus according to the third aspect, the data transmission control command transmitted from the data transmission control request unit to the data transmission apparatus is a data transmission control command. Is discriminated between a command for sending a packet carrying a packet and a command for sending an empty packet, using a specific n-bit (n is an integer of 1 or more) flag of a data sequence of a packet constituting the data transmission control command. Therefore, the flow control for issuing a transmission request to the data transmission side in accordance with the amount of data stored in the buffer on the data reception side is performed. By referring to the specific n bits, it is possible to perform transmission by transmitting a packet carrying data or transmitting an empty packet. There is an effect that it is possible to perform the flow control without the cross connection and location.

[0092] According to the data transmission method of the fifth aspect of the present invention, a data transmission apparatus for transmitting data in packet units and a data receiving apparatus for receiving data from the data transmission apparatus in packet units. In the data transmission method performed in the above, the data receiving device issues a data transmission control command for instructing whether to send a packet carrying data or to send an empty packet, and the data transmission device is based on the data transmission control command The data transmission control information storage means rewrites data transmission control information stored in the data transmission control information storage means for distinguishing whether to transmit a packet carrying data or to transmit an empty packet. While referring to the transmission control information, either a packet carrying data or an empty packet is sent. The effect of the data transmission method is obtained which can stop sending data without a connection to the data transmitting apparatus and the data receiving apparatus to the sectional.

According to the data transmission system of the sixth aspect of the present invention, when transmitting data in packet units, control for controlling whether to send a packet carrying data or an empty packet is performed. Data transmission control information storage means for storing information; and transmitting either the packet carrying the data or an empty packet based on the data transmission control information in the data transmission control information storage means, thereby transmitting the data. A data transmission device having a data transmission unit for performing the data transmission, a buffer for temporarily storing the received data when receiving data in packet units, and whether to continue receiving data according to the amount of data stored in the buffer. Means for determining data reception, and a packet having data loaded on the data transmitting apparatus according to the result of the data reception determining means. And a data transmission control requesting means for instructing whether to send an empty packet or an empty packet, wherein the data receiving device indicates whether to send a packet carrying data or to send an empty packet. The data transmission device issues a data transmission control command to discriminate whether to transmit a packet carrying data or to send an empty packet stored in the data transmission control information storage means based on the data transmission control command. In addition to rewriting the transmission control information, the data transmitting apparatus sends either a packet carrying data or an empty packet while referring to the data transmission control information every time a packet is transmitted. Data transmission can be controlled according to the amount of data stored on the data receiving side without changing the connection state between Data transmission system that allows data transmission without causing missed there is an effect to be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image of a connection between data transmission devices using a plug according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an IEEE 13 according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an internal configuration of a data transmission device including a 94 interface.

FIG. 3 is a diagram showing a format of data to be written in an output plug control register according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a flow control procedure according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a control operation of a control unit of the link layer device of the data transmission device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of an IEEE 1394 protocol.

FIG. 7 is a diagram showing a packet format of the AV protocol.

FIG. 8 is a diagram illustrating an image of a connection between data transmission devices using a conventional plug.

FIG. 9 is a diagram showing an arrangement of isochronous and asynchronous packets.

FIG. 10 is a diagram illustrating an internal configuration of a conventional data transmission device having an IEEE 1394 interface.

FIG. 11 is a diagram showing a format of a signal transmitted to an IEEE 1394 cable.

FIG. 12 is a diagram showing a format of data to be written into a conventional output plug control register.

FIG. 13 is a diagram showing a format of data to be written into a conventional input plug control register.

FIG. 14 is a flowchart illustrating a procedure of a conventional flow control.

FIG. 15 is a flowchart illustrating a control operation of a control unit of a link layer device in a conventional data transmission device on the reception side.

FIG. 16 is a flowchart illustrating a control operation of a control unit of a link layer device in a conventional data transmission device on a transmission side.

FIG. 17 is a diagram illustrating an example of a network configuration using an IEEE 1394 interface.

FIG. 18 is a diagram illustrating advantages of the IEEE 1394 interface.

[Explanation of symbols]

Reference Signs List 101 IEEE 1394 bus 102 Isochronous channel 103, 108, 109 Input plug control register 104, 110 Input master plug register 105 Output plug control register 106 Output master plug register 107, 111 AV equipment 200 Link layer device 200a Buffer unit 200b Transmission / reception unit 201 Host Controller Device 202 Host Interface 203 Asynchronous Transfer Buffer 204 Isochronous Transfer Buffer 205 Receive Buffer 206 Transmitter 207 Receiver 208 Physical Interface 209 Physical Layer Device 210 Cable 211 Register 212 Controller Unit 301 Online Flag Area 302 Broadcast connection counter area 303 Point-to-point connection counter area 304 Flow control area 305 Reserved area 306 Channel number area 307 Data rate area 308 Overhead ID area 309 Payload area

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

Claims (6)

[Claims] In a data transmitting apparatus for outputting data on a data transmission path, when transmitting data in packet units, control information for controlling whether a packet carrying data or an empty packet is transmitted. A data transmission control information storage means for storing the data transmission control information in the data transmission control information storage means, and transmitting data by outputting either a packet carrying the data or an empty packet. And a data transmission means for performing the transmission. 2. The data transmission device according to claim 1, wherein said data transmission control information storage means comprises a register provided in said data transmission device, and said register has a packet in which data is loaded. A data transmission device having a specific n-bit (n is an integer of 1 or more) flag for distinguishing whether to send an empty packet or an empty packet. 3. A data receiving apparatus for inputting data from a data transmission path, comprising: a buffer for temporarily storing received data when receiving data in units of packets; and a data buffer according to an amount of data stored in the buffer. Data reception determining means for determining whether to continue receiving data, and data for instructing the data transmitting apparatus to transmit a packet carrying data or an empty packet according to a result of the data reception determining means. A data receiving device comprising transmission control request means. 4. The data receiving apparatus according to claim 3, wherein the data transmission control command sent from the data transmission control requesting means to the data transmitting apparatus causes the packet carrying data to be transmitted or an empty packet to be transmitted. A data receiving apparatus, wherein whether a command is specified is determined by a specific n-bit (n is an integer of 1 or more) flag of a data sequence of a packet constituting the data transmission control command. 5. A method for transmitting data between a data transmitting apparatus for transmitting data in packet units and a data receiving apparatus for receiving data from the data transmitting apparatus in packet units, wherein the data receiving apparatus comprises: A data transmission control command for instructing whether to transmit a packet carrying a packet or an empty packet, and the data transmission device stores the data stored in the data transmission control information storage means based on the data transmission control command. The data transmission device rewrites the data transmission control information for discriminating whether to transmit the transmitted packet or the empty packet, and every time the data transmission device transmits the packet, the data transmission device refers to the data transmission control information, A data transmission method characterized by sending any one of the following packets: 6. When transmitting data in packet units,
Data transmission control information storage means for storing control information for controlling whether to transmit a packet carrying data or to transmit an empty packet; and based on the data transmission control information in the data transmission control information storage means, A data transmission device having data transmission means for transmitting data by outputting either a loaded packet or an empty packet, and a buffer for temporarily storing received data when receiving data in packet units And data reception determining means for determining whether to continue receiving data according to the amount of data stored in the buffer; and, based on a result of the data reception determining means, a packet carrying data on a data transmitting device. A data transmission control requesting means for instructing whether to transmit or transmit an empty packet, The data receiving device issues a data transmission control command for instructing whether to send a packet carrying data or to send an empty packet, and the data transmission device, based on the data transmission control command, has a data transmission control information storage unit. The data transmission control information for discriminating whether to send a packet carrying data or to send an empty packet to be stored is rewritten, and the data transmission device refers to the data transmission control information every time a packet is transmitted, and A data transmission system for transmitting either a packet carrying a packet or an empty packet.