Multiplex communications – Network configuration determination
Reexamination Certificate
1999-07-13
2001-08-14
Ton, Dang (Department: 2661)
Multiplex communications
Network configuration determination
C370S256000, C370S443000
Reexamination Certificate
active
06275473
ABSTRACT:
TECHNICAL FIELD
This invention relates to a bus management method in a communication system in which AV apparatus, such as a video tape recorder (VTR), a monitor or a tuner, are connected to a bus for exchanging digital video signals or digital audio signals.
BACKGROUND TECHNOLOGY
There has been entertained a communication system in which Av apparatus, such as a video tape recorder (VTR), a monitor or a tuner, are connected to a bus for exchanging digital video signals or digital audio signals.
FIG. 8
shows an example of such communication system, which is provided with a root node
21
, a leaf node
22
, a branch node
23
, a leaf node
24
and a leaf node
25
. Input/output ports between the nodes
21
and
22
, also referred to as nodes
21
-
22
, hereinafter the same, the nodes
21
-
23
, the nodes
23
-
24
and the nodes
23
-
25
, are connected by two sets of twist pair cables. The nodes
21
to
25
are the digital VTRs, tuners or personal computers, as discussed above, each having one or more input/output ports. Each node
21
to
25
has an amplifier and a relay enclosed therein. The communication system shown in
FIG. 8
is equivalent to a communication system in which the nodes
21
to
25
are connected to a bus
26
.
The structure shown in
FIG. 8
is a hierarchical structure in which the nodes
22
and
23
are connected in the lower layer relative to the node
21
and the nodes
24
and
25
are connected in the lower layer relative to the node
23
. In other words, the node
21
is a master node for the nodes
22
and
23
, while the node
23
is a master node for the nodes
24
and
25
. The sequence for determining such hierarchical structure is now explained.
If the nodes
21
-
22
,
21
-
23
,
23
-
24
and
23
-
25
are connected by cables, the node only one input/output port of which is connected to an other node notifies the node to which it is connected that the latter node is the master node. In the case of
FIG. 8
, the nodes
24
and
25
notify the node
23
of the fact that the node
23
is the master node, while the node
22
notifies the node
21
of the fact that the node
21
is the master node.
The node plural input/output nodes of which are connected to other nodes notifies a node other than the node which has notified the firstly-stated node that the firstly-stated node is the master node that such other node is the master node. In the case of
FIG. 8
, the node
23
notifies the node
21
that the node
21
is the master node, while the node
21
notifies the node
23
that. the node
23
is the master node. Since in such case the nodes
21
,
23
notify each other that the counterpart node is the master node, the node which has made such notification first becomes the master node.
FIG. 8
shows a case in which the node
21
has become the master node.
The sequence of according an address to each node is explained. Basically, the node address is accorded by the master node permitting an address to be accorded to a slave node. If there are plural slave nodes, addresses are accorded in the order of the smaller port numbers to which the slave nodes are connected.
In
FIG. 8
, in which the node
22
is connected to a port #1 of the node
21
and the node
23
is connected to a port #2 of the node
22
, the node
21
permits an address to be accorded to the node
22
. The node
22
accords the address (i) to itself and transmits data indicating that the address (i) has been accorded to itself over a bus
26
. The node
21
then permits the node
23
to set its own address. The node
23
permits an address to be accorded to the node
24
connected to its port #1. The node
24
accords the address (ii) to itself. The node
23
permits an address to be accorded to a node
25
connected to its port #2. The node
25
accords an address (iii) to itself. After having accorded addresses to its slave node
24
and slave node
25
, the node
23
accords an address (iv) to itself. After having accorded addresses to its slave node
22
and slave node
23
, the node
21
accords an address (v) to itself.
With the present communication system, it is possible to carry out synchronous communication or continuous communication at a constant data rate and asynchronous communication for transmitting control commands, for example, non-periodically, that is whenever the necessity arises.
With the present communication system, communication is carried out at a communication cycle having a pre-set period, such as 125 &mgr;s, as shown in FIG.
10
. The communication cycle starts with a cycle start packet csp, followed by a period for transmitting a packet for synchronous communication. By affixing channel numbers 1, 2, 3, . . . N to the respective packets for synchronous communication, plural synchronous communication cycles may be carried out. For example, if the channel 1 is allocated to the communication from the node
22
to the node
23
, communication is carried out by the node
22
transmitting the packet for synchronous communication having the channel number 1 directly after the cycle start packet csp and by the node
23
monitoring the bus
26
and fetching the packet for synchronous communication having the channel number
1
. Similarly, the communication from the node
24
to the node
21
can be accorded to the channel
2
, while the packet of a channel can be received by plural nodes.
If plural synchronous communication cycles are carried out, it is attempted to transmit the packets for synchronous communication over plural channels directly after the cycle start packet cps. In such case, the packet of synchronous communication of a channel is first transmitted by arbitration means (such as CSMA/CD) as determined by the bus
26
. The packets of synchronous communication of other channels are then transmitted sequentially.
After termination of transmission of the packets of synchronous communication of all of the channels, the time interval until the next cycle start packet csp is employed for asynchronous communication. To the packets for asynchronous communication (packets A and B in
FIG. 10
) are affixed addresses of the transmitting node and the receiving node. The respective nodes fetch the packets having the addresses proper to the nodes affixed thereto.
Since the details of the above-described communication system are publicized as “IEEE P1394 Serial Bus Design Statement, they are not explained herein specifically.
In order for the above-described communication system to operate correctly, it is necessary for the respective synchronous communication packets to have different channel numbers, while it is necessary for the sum total of the communication time of the synchronous communication packets of the respective channels not to exceed the period of the synchronous communication. To this end, it is necessary to check before the start of synchronous communication of a node that the communication capacity necessary for the communication is available on the bus and to have an un-used channel allocated for the communication if there is any residual communication capacity in the bus.
For supervising the communication capacity and the channel number employed for synchronous communication, it is commonplace practice that one of the nodes connected to a bus become a bus management node and to effect required management. In such case, other nodes indicate the communication capacity desired to be employed to the bus management node, using the asynchronous communication packet, and require channels to be allocated to them. The bus management node checks if the communication capacity in use added to the communication capacity newly requested does not exceed the maximum communication capacity of the bus. If the sum is not in excess of the maximum communication capacity of the bus, the bus management node notices the channel number and the effect of permission of synchronous communication. If the sum is in excess of the maximum communication capacity of the bus, the bus management node notices that the channel allocation is not permitted. Afte
Hayashi Minobu
Kubota Ichiro
Matsuno Katsumi
Shima Hisato
Frommer William S.
Frommer Lawrence & Haug LLP.
Pizarro Ricardo M.
Polito Bruno
Sony Corporation
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