Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1999-02-19
2004-02-10
Vincent, David (Department: 2661)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S248000
Reexamination Certificate
active
06690648
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data communication system, data communication method, data communication apparatus and digital interface, particularly to a network in which information data (including image data) and command data are mixed to perform communication at high speed and a communication protocol applicable to the network.
2. Related Background Art
Hard discs and printers have heretofore had highest frequencies of use among peripheral apparatuses of personal computers (hereinafter referred to as PC). These peripheral apparatuses are connected to PC via dedicated input/output interfaces, SCSI (small computer system interfaces) or other general-purpose digital interfaces.
On the other hand, in recent years, digital cameras, digital video cameras and other AV (Audio/Visual) apparatuses have gained public attention as PC peripheral apparatuses. The AV apparatuses are also connected to PC via dedicated interfaces.
FIG. 1
is a view showing a conventional communication system constituted of PC and AV apparatus.
In
FIG. 1
, numeral
101
denotes an AV apparatus or digital camera,
102
denotes PC, and
103
denotes a printer.
The digital camera
101
comprises a memory
104
in which a photographed image is compressed and recorded; a decoding unit
105
for expanding and decoding the compressed image data recorded in the memory
104
; an image processing unit
106
; a D/A converter
107
; a display
108
comprising EVF; and a dedicated digital I/O unit
109
for connecting the digital camera
101
and the PC
102
.
The PC
102
comprises a dedicated digital I/O unit
110
for connecting the PC
102
and the digital camera
101
; an operation unit
111
comprising a keyboard, a mouse and the like; a decoding unit
112
for expanding and decoding the compressed image data; a display
113
; a hard disc
114
; RAM or another memory
115
; an MPU
116
; a PCI bus
117
; and an SCSI interface
118
for connecting the PC
102
and the printer
103
.
The printer
103
comprises an SCSI interface
119
for connecting the printer
103
and PC
102
; a memory
120
; a printer head
121
; a printer controller
122
for controlling operation of the printer
103
; and a driver
123
.
In the conventional communication system, since the digital interface or digital I/O unit
109
of the digital camera
101
is not compatible with the digital interface or SCSI interface
110
of the printer
103
, they cannot be directly interconnected. For example, a still image needs to be transmitted to the printer
103
from the digital camera
101
necessarily via the PC.
Moreover, in the conventional dedicated interface or the SCSI interface, when a large volume of data such as still images or moving images held by the AV apparatus are handled, many problems are caused that a data transfer rate is low, communication cable for parallel communication is thick, there are only a small number of types of connectable peripheral apparatuses, connection system is limited and that real-time data transfer cannot be performed.
Known as one of next-generation high-speed high-performance digital interfaces to solve the problems is an IEEE (The Institute of Electrical and Electronics Engineers, Inc.) 1394-1995 standards.
A digital interface conforming to the IEEE 1394-1995 standards (hereinafter referred to as the 1394 interface) has the following characteristics:
(1) data transfer rate is high;
(2) real-time data transfer system (i.e., Isochronous transfer system) and Asynchronous transfer system are supported;
(3) connection structure (topology) with a high degree of freedom can be constructed; and
(4) plug-and-play function and hot-line plug/unplug function are supported.
In the IEEE 1394-1995 standards, although a physical, electric structure of a connector, two basic data transfer systems, and the like are defined, it is not defined what type of data is transmitted/received based on what communication protocol in what data format.
Moreover, in Isochronous transfer system of the IEEE 1394-1995 standards, since a response to a sending packet is not defined, there is no guarantee that each Isochronous packet is surely received. Therefore, when a plurality of continuous data are to be securely transferred, or when one file data is segmented into a plurality of data to be securely transferred, Isochronous transfer system cannot be used.
Furthermore, in Isochronous transfer system of the IEEE 1394-1995 standards, even when there is a vacancy in a transfer band, the total number of communications is limited to 64. Therefore, when a large number of communications are performed in a little transfer band, Isochronous transfer system cannot be used.
Additionally, in the IEEE 1394-1995 standards, if bus rest occurs in response to the turning ON/OFF of a node power supply, the connection/disconnection of a node, or the like, data transfer has to be interrupted. In the IEEE 1394-1995 standards, however, when the data transfer is interrupted by the bus reset or an error at the time of transmission, it cannot be known what content of data is lost. Furthermore, in order to return once interrupted transfer, a very intricate communication procedure needs to be carried out.
Here, the bus reset indicates a function of automatically performing the recognition of a new topology and the setting of an address (node ID) allotted to each node. Therefore, the plug-and-play function and the hot-line plug/unplug function can be provided in the IEEE 1394-1995 standards.
Moreover, in the communication system conforming to the IEEE 1394-1995 standards, a communication protocol has not been concretely proposed for segmenting into one or more segment data and continuously transferring a relatively large amount of object data (e.g., still image data, graphic data, text data, file data, program data, and the like) which are required to have no real-time properties but have reliability.
Furthermore, in the communication system conforming to the IEEE 1394-1995 standards, a communication protocol has not been either concretely proposed for realizing data communication among a plurality of apparatuses using a communication system in which data is asynchronously broadcast.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the aforementioned problems.
Another object of the invention is to provide a technique in which object data requiring no real-time properties can continuously and securely be transferred in a data communication system, data communication method, data communication apparatus and digital interface.
A further object of the invention is to provide a technique in which a time interval between continuously transferred data can be optimized in a data communication system, data communication method, data communication apparatus and digital interface, and unnecessary interruption in a series of data transfer can easily, securely and efficiently be prevented.
A still further object of the invention is to provide a technique which can realize an efficient data communication in such a manner that unnecessarily occurring retry can easily and securely be prevented in a data communication system, data communication method, data communication apparatus and digital interface.
As a preferred embodiment for such objects, the present invention discloses a data communication system comprising: a source node for performing asynchronous communication at least once to transfer data comprising one or more segments; one or more destination nodes for receiving the data transferred from the source node; and a controller for setting a logical connection relationship between the source node and the one or more destination nodes, wherein at least one of the source node and the controller controls a timing for performing the asynchronous communication.
As another preferred embodiment, the present invention discloses a data communication system comprising: a source node for performing broadcast communication at least once to transfer data comprising one or more segments based on a logic
Hatae Shinichi
Kobayashi Takashi
Niida Mitsuo
Ohnishi Shinji
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Vincent David
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