Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
2000-07-26
2001-08-14
Etienne, Ario (Department: 2155)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S120000, C710S240000, C709S227000
Reexamination Certificate
active
06275889
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a connection control apparatus for use in a communication network and more particularly to a connection control apparatus for controlling, in a network with a bus such as a high-speed serial bus IEEE 1394 (refer to “IEEE Standard for a High Performance Serial Bus”, IEEE Standard 1394-1995) to which a personal computer, its peripheral device and/or an audio visual device (hereinafter referred to as a “AV device”) can be connected, those devices connected to such a bus.
In recent years, personal computers become common in homes, and various techniques have been and are being developed for improving the usability of such personal computers by their users. It has also become common for audio and visual information to be treated in digital form. For example, data from a digital video camera can be processed in a personal computer at home. Under such circumstances, new bus systems such as a USB (Universal Serial Bus) and an IEEE 1394 bus have been proposed as new technology for improving the connectability between a computer and its peripheral device, such as a printer or an image scanner, and actually been brought to market in some fields.
As compared to the USB that needs interfacing by a computer for the connection between its peripheral devices, the IEEE 1394 bus does not need any interfacing by a computer for such connection. The latter can therefore be used not only for connecting a personal computer to its peripheral devices such as a printer, a hard disc drive, or an image scanner, but also for transferring main and control signals among video devices such as a digital video camera and audio devices. Since it is thus possible to construct a network by connecting a plurality of devices complying with the IEEE 1394 standard (hereinafter referred to simply as “1394 devices”), this standard is considered to be a promising standard for use in a LAN for home networking.
FIG. 9
shows, by way of example, a network constructed to connect AV devices, which are 1394 devices, using an IEEE 1394 bus. In the example shown in
FIG. 9
, five AV devices
80
a
to
80
e
all of which are 1394 devices are connected to an IEEE 1394 bus B
10
. In order to associate an isochronous channel when transferring data between AV devices, each AV device is provided with a master plug register (MPR) and a plug control register (PCR) as prescribed in the IEC 61883 standard (“Consumer Audio/Video Equipment—Digital Interface—Part 1: General”, Reference Number CEI/IEC 61883-1: 1998).
Each of these registers comprises an input and an output register for audio data and video data, and each master plug register is provided with an input master plug register (iMPR) and an output master plug register (oMPR), while each plug control register is provided with an input plug control register (iPCR) and an output plug control register (oPCR).
In the example shown in
FIG. 9
, the AV devices
80
a
to
80
d
comprise iMPRs
82
a
to
82
d
, respectively, and the AV device
80
e
comprises an oMPR
84
. The iMPR
82
a
to
82
d
comprise iPCRs
86
and
88
, an iPCR
90
, an iCPR
92
and iCPRs
94
and
96
, respectively, and the oMPR
84
comprises an oPCR
98
. In
FIG. 9
, shown at C
10
is an isochronous channel that is established to transmit or receive data when an isochronous transfer of the data should take place between AV devices connected to the IEEE 1394 bus B
10
.
FIG. 10
illustrates detailed formats for the above-described registers, wherein (a) shows the format for the output master plug register (oMPR), (b) the format for the input master plug register (iMPR), (c) the format for the output plug control register (oPCR) and (d) the format for the input plug control register (iPCR). These formats have been standardized. The numerals shown at the bottom of each format represent the numbers of bits of respective data constituting the relevant format.
Each of the AV devices
80
a
to
80
e
comprises a respective single one of the iMPRs
82
a
to
82
d
and oMPR
84
, each of which manages the number of plug control registers in a respective one of the AV devices, i.e., iPCRs
86
to
96
and oPCR
98
. The number of oPCRs and iPCRs which can be present in one AV device is thirty-one at maximum. The oPCR and IPCR include, for the information required to establish a connection, fields FC
2
and FD
2
each for storing information indicating the presence of a broadcast connection, fields FC
3
and FD
3
each for storing information indicating the number of point-to-point connections, fields FC
5
and FD
5
each for storing information indicating an isochronous channel number and so on, respectively. The oPCR further includes a field FC
6
for storing information indicating a transfer rate of isochronous data flow and a field FC
8
for storing information indicating a bandwidth. Addresses of the registers in which the MPR and PCR are described are described, as shown in
FIG. 11
, in addresses from FF FF F
0
09
00
h to FF FF F
0
09
FFh (h represents hexadecimal notation) within a CSR (Command and Status Register) space defined in the IEEE 1394 standard.
FIG. 11
illustrates a structure of the CSR space according to the IEEE 1394 standard.
For isochronous data output from an AV device, a path for sending the isochronous data between AV devices can be determined by making a proper setting to these PCRs, whereby it is possible to have a data transfer made between any arbitrary AV devices.
Referring again to
FIG. 9
, the concept of connection utilizing PCRs will be described. The connection utilizing PCRs is categorized into two types, i.e., a point-to-point connection and a broadcast connection.
The point-to-point connection is a connection in which an oPCR of an AV device is connected through an isochronous channel to an iPCR of another AV device. This type of connection corresponds, for example, to the data flow between the oPCR
98
of the AV device
80
e
and the iPCR
90
of the AV device
80
b
shown in FIG.
9
. This connection is protected so that the relevant registers can be rewritten only by the device that established this connection, or by the relevant control application program.
It is also possible to have a plurality of point-to-point connections present with respect to the same single PCR. In the example shown in
FIG. 9
, this corresponds to the connection between the oPCR
98
of the AV device
80
e
and the iPCR
94
of the AV device
80
d
. In this example, there are three point-to-point connections which use the same isochronous data flow.
The broadcast connection is composed of a broadcast-out connection for associating one oPCR of an AV device only with one isochronous channel and a broadcast-in connection for associating one iPCR of another AV device only with one isochronous channel.
In the example of
FIG. 9
, the association of the oPCR
98
of the AV device
80
e
with a broadcast channel number (usually set to “63”) for the isochronous data is a broadcast-out connection, while the association of the iPCR
92
of the AV device
80
c
with the broadcast channel number for the isochronous data is a broadcast-in connection.
These two types of broadcast connections are established independently of the mutual relation in the condition of the sender and the recipient. Any device other than those devices or control application programs which have established the broadcast connection can alter (or rewrite) the PCR not only to cut the connection but also to allocate the broadcast isochronous channel of the currently transferring device.
The data transmission/reception after the establishment of a connection between AV devices can be started by controlling the sending and receiving AV devices by AV/C (Audio Video Control) commands defined in “AV/C Digital Interface Command Set Version 3.0”, 1394 Trade Association, Apr. 15, 1998 or “AV/C Tape Recorder/Player Subunit Specification Version 2.1”, 1394 Trade Association, Jan. 11, 1998. As AV/C commands, a play command, a stop command, a fast forward command, a rewind command, a record
Etienne Ario
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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