Electrical computers and digital data processing systems: input/ – Intrasystem connection – Protocol
Reexamination Certificate
1999-12-30
2002-09-24
Ray, Gopal C. (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Protocol
C710S107000, C710S305000
Reexamination Certificate
active
06457079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication apparatus comprising means for allocating alternate designation information such as a virtual address or the like to each function unit, and a communication system comprising the above-mentioned two communication apparatuses which are communicated with each other. In particular, the present invention relates to a communication apparatus, for example, computers, peripheral equipments such as a printer or the like, various domestic digital equipments such as a digital still camera or the like, and a communication system comprising the above-mentioned two communication apparatuses which are communicated with each other via a serial bus conformed to IEEE 1394.
2. Description of the Related Art
For example, an ANSI X3.131-1986 Small Computer System Interface proposed by the ANSI (American National Standards Institute, Inc.) has been widely used thus far as an interface for carrying out data transmission between a personal computer, and peripheral equipments connected with the personal computer.
However, in so-called parallel SCSI standard of the above-mentioned interface standards, there is no rule relating to many matters such as a shape of a connector or cable, an operation of connecting equipments without power supply. As a result, problems arise in compatibility and convenience accompanying with popularization of the personal computer.
Moreover, in comparison with the time when the above-mentioned parallel SCSI standard has been proposed, recently, various domestic digital equipments are popularized. Further, a general household also requires a high speed interface which is adaptable for transmitting acoustic and image digital signal data.
Under such circumstances, some next-generation interface standards have been already proposed, and then, the IEEE 1394 interface is employed as an interface for transmitting data at a high speed between computers and peripheral equipments and between apparatuses including domestic equipments, and thus, digital equipments using the IEEE 1394 interface have been started to be merchandised.
The IEEE 1394 interface standard is proposed by IEEE (The Institute of Electrical and Electronics Engineers, Inc.), and then, is prescribed as IEEE Std. 1394-1995 IEEE Standard for a High Performance Serial Bus. More specifically, the IEEE 1394 interface standard is a very useful serial interface standard taking the use in a general household into consideration, that is, an interface conformed to the standard has a high transfer speed of several 100 Mbits/second, and supports a synchronous transfer, a hot-line insertion and drawing and a connection topology having a high degree of freedom.
For example, Japanese Patent Laid-open Publication (Kokai) No. 10-93623 discloses a technique of employing the above-mentioned IEEE 1394 interface.
As disclosed in the above publication, in the case of carrying out a digital data transmission with the use of a packet adding a destination information to a predetermined data block into which a digital data is divided, in order to improve the reliability of data transmission, when a packet transmitted from a transmitter equipment is received by a receiver equipment, the receiver equipment returns an acknowledgment signal indicative of a receiving state of the packet to the transmitter equipment of the printer apparatus
2
a
, and then, retransmits the packet from the transmitter equipment as the necessity arises.
Also, in the IEEE 1394 interface, there is the case where the above acknowledgment signal from the receiver equipment to the transmitter equipment is returned with respect to a request packet for request for an operation thereof.
For example, in a packet communication between a personal computer
1
and a printer apparatus
2
a
mutually connected the IEEE 1394 interface, as shown in
FIG. 3
, a request packet for requiring a predetermined operation is transmitted from the personal computer
1
to the printer apparatus
2
a
, and then, when the request packet is received by the printer apparatus
2
a
, the printer apparatus
2
a
returns an acknowledgment signal ACK indicative of a receiving state of the request packet to the personal computer
1
.
The acknowledgment signal ACK includes information data for informing retransmission necessity and completion of reception of the printer apparatus
2
a
. For example, in the case where an acknowledgment signal ACK which requires retransmission is received by the personal computer
1
, the same request packet is retransmitted from the personal computer
1
to the printer apparatus
2
a
. Then, in the case where a completion of reception is informed to the personal computer
1
by means of the above acknowledgment signal ACK, the printer apparatus
2
a
carries out a predetermined operation such as a print operation. Therefore, the personal computer
1
is in a waiting state until a response packet corresponding to the above request packet is transmitted from the printer apparatus
2
a.
Further, when a predetermined operation is completed in the printer apparatus
2
a
, a response packet including the above predetermined operation result is transmitted from the printer apparatus
2
a
to the personal computer
1
. When the response packet is received by the personal computer
1
, an acknowledgment signal ACK indicative of a retransmission request or process completion is returned from the personal computer
1
to the printer apparatus
2
a
. In this case, if the above acknowledgment signal ACK is indicative of a retransmission request, the same response packet is retransmitted from the printer apparatus
2
a
to the personal computer
1
. On the other hand, if the above acknowledgment signal ACK is indicative of process completion, the printer apparatus
2
a
is set to an opened state for the next process.
By the way, as one of application protocols in the IEEE 1394 interface is provided an SBP-2 (Serial Bus Protocol 2). In order to explain the SBP-2, a relation between the layer structure of the IEEE 1394 interface and the SBP-2 is shown in
FIG. 4
, which shows the personal computer
1
and the printer apparatus
2
a
are connected with each other via a serial data bus
3
.
The layer structure of the IEEE 1394 interface layer
100
or
200
is fundamentally comprised of three layers of a physical layer
101
or
201
, a link layer
102
or
202
, and a transaction layer
103
or
203
as shown in FIG.
4
. The SBP-2 belongs to a transport layer
104
or
204
at a layer position higher than that of the transaction layer
103
or
203
. For example, the SBP-2 has not only a function of efficiently transferring commands and data among various kinds of apparatuses or devices (referred to as nodes hereinafter) such as optical disk drive units, DVD drive units, magnetic tape drive units, scanners, digital cameras or the like, but also another function of notifying an application layer processing unit higher than the SBP-2, of operating states of commands, the results thereof, a state indicating whether or not data transfer is completed, or the like. It is to be noted that an application layer
105
or
205
is provided above the transport layer
104
or
204
of the SBP-2.
In the SBP-2, there is provided a node such as a scanner, a digital camera or the like, each having a function of not only issuing management request commands such as login for a connection request, a logout of completion of connection or the like, but also real commands such as a data read command, a data write command or the like, and this node is called an “initiator” apparatus. On the other hand, there is further provided another node such as an optical disk drive unit, a DVD drive unit, a CD-ROM drive unit, a printer, or the like, each having a function of receiving a command from the initiator apparatus and actually performing a process, and this another node is called a “target” apparatus. Communication is carried out between the initiator apparatus and the target apparatus.
With respect to the targ
Akashita Shoji
Hanaoka Kunihiro
Kurose Mitsukazu
Tomioka Osamu
(Kobe Steel, Ltd.)
Ray Gopal C.
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