Multiplex communications – Channel assignment techniques – Carrier sense multiple access
Reexamination Certificate
1999-06-10
2003-10-21
Vanderpuye, Kenneth (Department: 2732)
Multiplex communications
Channel assignment techniques
Carrier sense multiple access
C370S447000
Reexamination Certificate
active
06636526
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to node-to-node communications performed in serial-bus networks using serial buses, which connect personal computers (or PCs) and electronic apparatuses together. Specifically, this invention relates to signal sending-and-receiving circuits applicable to long-distance ports of nodes of the serial-bus networks and Self ID processes for initialization of the serial-bus networks in the node-to-node communications. Herein, the serial-bus networks are designed based on an architecture using a specific kind of serial bus or equivalence of such serial bus, which is standardized by “IEEE Std. 1394-1995” (i.e., IEEE Standard for a High Performance Serial Bus, where “IEEE” is an abbreviation for “Institute of Electrical and Electronics Engineers”), for example.
This application is based on Patent Application No. Hei 10-172343 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Engineers have proposed networks using serial buses in transmission of control signals and main signals between peripheral devices (e.g., hard disk units and scanners) and/or electronic devices. Herein, the electronic devices contain terminal devices facilitating serial buses, which will be called “nodes”.
For example, the paper of Japanese Patent Application, Publication No. Hei 8-293879 discloses the technology related to the electronic devices such as the personal computers and digital television receivers which are connected with P1394 serial buses, wherein operation mode control is performed to avoid hang-up at a bus reset mode.
The aforementioned nodes have various kinds of state machines, functions of which can be mainly classified into four types. Namely, there are provided three processes for initialization of networks (i.e., Bus Reset process, Tree ID process and Self ID process) as well as a process (i.e., Normal process) which performs “normal” communications between nodes.
Each of the processes defines multiple states. For example, the Bus Reset process defines two states, i.e., “R
0
” (Reset Start) and “R
1
” (Reset Wait).
In addition, the Tree ID process defines four states, i.e., “T
0
” (Tree ID Start), “T
1
” (Child Handshake), “T
2
” (Parent Handshake) and “T
3
” (Root Contention).
Further, the Self ID process defines five states, i.e., “S
0
” (Self ID Start), “S
1
” (Self ID Grant), “S
2
” (Self ID Receive), “S
3
” (Send Speed Capabilities), “S
4
” (Self ID Transmit). Furthermore, the Normal process defines seven states, i.e., “A
0
” (Idle), “A
1
” (Request Test), “A
2
” (Request Delay), “A
3
” (Request), “A
4
” (Grant), “A
5
” (Receive) and “A
6
” (Transmit).
The state machine performs state transition in response to a signal (or signals) given from an adjoining node connected thereto. Next, a description will be given with respect to node-to-node communications, which cause transition of states of the state machine.
It is possible to construct a network by using a serial bus, which uses two pairs of STPs (i.e., Shielded Twisted Pairs) within a prescribed range of node-to-node distances up to 4.5 m, for example.
FIG. 7
shows an example of node-to-node communication effected between two nodes, i.e., “Node
1
” and “Node
2
”, which are connected together by two pairs of “twisted wire pairs” (referred to as “TPA” and “TPB” respectively). Specifically,
FIG. 7
shows contents of signals communicated between the nodes over a cable. Herein, TPA and TPB cross with each other. In
FIG. 7
, TPA at Node
1
corresponds to TPB at Node
2
, while TPB at Node
1
corresponds to TPA at Node
2
. In an initial state, both of Node
1
and Node
2
output Idle signals, where (TPA, TPB)=(Z,Z). Table
1
shows a result of collision effected between “Parent_notify” signal (
0
,Z) output from Node
1
and an output (Z,Z) of Node
2
. That is, Table
1
indicates that as the result of the collision, Node
2
receives a state (Z,
0
) on the cable. Incidentally, “send signal” of Node
1
in Table
1
represents a signal which is observed from Node
2
. Table
2
shows a result of collision effected between “Parent_notify” signal (
0
,Z) output from Node
1
and “Child_notify” signal (Z,
1
) output from Node
2
. That is, Table
2
indicates that as the result of the collision, Node
1
receives a state (
0
,
1
) on the cable. Incidentally, “send signal” of Node
2
in Table
2
represents a signal which is observed from Node
1
. As described above, half duplex communication is performed between the nodes of the serial-bus network using the twisted wire pairs.
Next, a description will be given with respect to operations of nodes in accordance with a Self ID process with reference to a network architecture shown in FIG.
8
. Herein, there provided four nodes, namely, Node
1
, Node
2
, Node
3
and Node
4
, wherein both of Node
2
and Node
3
function as repeaters, each of which is configured using only a physical (link) layer (or PHY layer) consisting of a state machine and ports. Node
1
and Node
4
have other layers up to application layers in addition to the PHY layers. Incidentally, this invention exclusively relates to improvements in the PHY layers. Therefore, a description is omitted with regard to the other layers such as LINK layers, transaction layers and application layers. In the PHY layer, the DS port effects DS modulation (where “DS” is an abbreviation for “Data Strobe”) on signals given from the state machine, so that modulated signals are output on the twisted wire pairs TPA and TPB. In addition, the DS port demodulates signals given from the twisted wire pairs, so that demodulated signals are transferred to the state machine.
FIG. 9
shows an example of transition of states in the state machine in accordance with the conventional Self ID process. Herein, “S
0
” designates an initial state of the Self ID process. Upon receipt of a grant signal, the state machine performs a state transition from the state S
0
to a state “S
1
”. Herein, the state S
1
is a state that the state machine sends or receives the grant signal. Under a condition of “all_child_port_identified=true” where the state machine receives signals declaring ends of the Self ID processes from all ports linked to child nodes, the state machine performs a state transition from the state S
1
to a state S
4
. On the other hand, if the state machine receives a Data_prefix signal from a port linked to the child node, it performs a state transition from the state S
1
to a state “S
2
”. Herein, the state S
2
is a state that the state machine receives a Self ID packet. When the state machine ends reception of the packet and detects an Idle signal on a receive port, it performs state transition from the state S
2
to the state S
0
. The state S
4
is a state that the state machine sends the Self ID packet. So, when the state machine ends the Self ID process at completion in sending of the Self ID packet, it performs a state transition from the state S
4
to a state A
0
which corresponds to the Normal process. Incidentally, a description will be omitted with regard to a state S
3
and its transition conditions, which are not directly related to the present invention.
Next, a description will be given with respect to operations of the Self ID process under an assumption that Node
1
serves as a root designating a central node of the network with reference to
FIG. 10
, which also shows transition of states of the state machine in Node
3
. Each of Nodes
2
,
3
and
4
receives a grant signal (grant
1
) from the root (i.e., Node
1
). Upon receipt of the grant signal, each of them sends a Self ID packet representing information thereof. At first, Node
1
sends “grant
1
”, so that Nodes
2
and
3
repeat (or relays) it. Upon receipt of grant
1
, Node
3
performs a state transition from S
0
to S
1
, so that it successively sends the grant signal (grant
1
) to Node
4
. Upon receipt of the grant
1
, Node
4
sends a Self ID packet
1
to follow a Data_prefix signal represent
NEC Corporation
Vanderpuye Kenneth
LandOfFree
Signal sending-and-receiving circuit and self ID process for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Signal sending-and-receiving circuit and self ID process for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Signal sending-and-receiving circuit and self ID process for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3165760