Multiplex communications – Fault recovery – Bypass an inoperative channel
Reexamination Certificate
1999-08-19
2003-07-08
Chin, Wellington (Department: 2731)
Multiplex communications
Fault recovery
Bypass an inoperative channel
C370S464000
Reexamination Certificate
active
06590863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an operation mode changing-over method wherein each of a plurality of nodes connected to a common multiplex transmission path can have its operation mode changed over between a multiplex communication mode in which multiplex communication is made via an interface for use in multiplex transmission that is provided in the node and a sleep mode in which the interface is kept inoperative, and to a multiplex transmission apparatus for realizing the same. More particularly, the invention concerns an operation mode changing-over method which enables the operation mode to be changed over from the sleep mode to the multiplex communication mode without providing a transmission line for exclusive use on a seizing signal, and a multiplex transmission apparatus for realizing the same.
2. Related Art
In recent years, a multiplex transmission apparatus for performing multiplex communication is loaded on a vehicle, and this multiplex transmission apparatus is constructed with a plurality of nodes being connected to a common multiplex transmission path. Each node has provided therein an interface for use in multiplex communication for multiplexing data and making transmission and reception thereof, whereby transmission and reception of data are made between micro-controllers provided in their relevant nodes via the multiplex communication interface and the multiplex transmission path.
In order to maximally suppress the power consumption, each node has a changing-over function for making a changeover between a multiplex communication mode in which multiplex communication is performed via the multiplex transmission interface and a sleep mode in which the multiplex transmission interface is kept inoperative to decrease the current consumption.
At an ordinary time, the node is operated in the sleep mode to thereby suppress useless power consumption. When prescribed activation conditions have been satisfied, the operation mode is changed over, using a seizing signal, to the multiplex communication mode in which to permit the multiplex transmission interface to operate the micro-controller into its operational state.
FIG. 1
is a construction block diagram illustrating a conventional example of this type of multiplex transmission apparatus. In a multiplex transmission apparatus illustrated in
FIG. 1
, a plurality of nodes
102
a
to
102
n
are connected to a multiplex transmission path
103
. A transmission line
104
for exclusive use on a seizing signal is provided separately from the multiplex transmission path
103
that is a data transmission line. Whereby, the node
102
a
transmits a seizing signal to all other nodes
102
b
to
102
n
via the transmission line
104
for exclusive use on a seizing signal.
When having received a seizing signal, each of the nodes
102
b
to
102
n
has its operation mode changed over from a sleep mode to a multiplex communication mode. As a result of this, every one of the nodes
102
a
to
102
n
has its operation mode transferred from the sleep mode to the multiplex communication mode, whereby bi-directional communication can be made between each node through the multiplex transmission path
103
.
However, in the conventional multiplex transmission apparatus illustrated in
FIG. 1
, a transmission line for exclusive use on a seizing signal had to be provided separately from the multiplex transmission path. For this reason, there was the problem that the wire reduction effect resulting from the utilization of multiplex communication would be impaired.
On this account, as a technique that has solved this problem, a multiplex transmission apparatus that is described in Japanese Patent Application Laid-Open Publication No. H5-183562 is known. As illustrated in
FIG. 2
, in the multiplex transmission apparatus that is described in this Laid-Open Publication, nodes
114
a
,
114
b
, and
114
c
are connected to annular first and second transmission paths
112
and
113
, whereby a controller
117
within each node
114
a
,
114
b
, and
114
c
transmits and receives a signal to and from another corresponding one via a multiplex module
115
.
An activation circuit
120
for causing a seizing signal, which changes over the operational condition of the controller
117
from the sleep mode to the multiplex communication mode, to be input and output with respect to each corresponding one of the nodes
114
a
,
114
b
, and
114
c
is connected to the first transmission path
112
. The activation circuit
120
has an input transistor
121
for inputting the seizing signal and an output transistor
122
for outputting the seizing signal.
In this construction, the controller
117
in the node
114
a
activates the multiplex module
115
and thereby activates the node
114
a
. On the other hand, the controller
117
outputs a seizing signal from its output terminal
126
to thereby make the output transistor
122
of the activation circuit
120
“on” and thereby activate the nodes
114
b
and
114
c
. Namely, the nodes
114
b
and
114
c
can be activated by the input transistors
121
thereof being made “on”. The controller
117
of the node
114
a
, when a prescribed waiting time length T
0
has lapsed, outputs a transmission request frame via the multiplex module
115
and thereafter is transferred to the multiplex communication mode.
However, the multiplex transmission apparatus that is described in Japanese Patent Application Laid-Open Publication No. H5-183562 had the following problems.
(1) First, when at the time of the multiplex communication mode the input transistor
121
that is a reception portion of the starting circuit
120
is made “on”, the current consumption inconveniently increases and the impedance of the transmission path varies. Namely, as a result of the “on” operation of the input transistor
121
, the impedance of the reception end decreases and this impedance ceases to match with the impedance of the transmission path. This is followed by the new problems that the signal is inconveniently reflected, the waveforms are distorted, the transmission data changes itself into a meaningless form, and the radiation noises increase.
(2) Further, at the time of activation, awaiting length of time is provided in order to prevent the element from being destroyed due to the phenomenon that the output transistor
122
that is a transmission portion and the output of the multiplex module
115
are short-circuited. This deteriorated the responsiveness to starting.
(3) Furthermore, since the output transistor
122
that is a transmission portion was provided in the activation circuit
120
, the cost was increased by that extent.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an operational mode changing-over method that makes it possible to enhance the responsivity to activation without causing a increase in the current consumption and causing the occurrence of waveform distortions and that can be realized with an inexpensive construction, and a multiplex transmission apparatus for realizing the same.
To attain the above object, according to an aspect of the present invention, there is provided a multiplex transmission apparatus wherein a plurality of nodes are connected to a multiplex transmission path; each node performs communication, via an interface portion for use in multiplex transmission that has been provided therein, with another node; and each node has its mode that is changeable over between a multiplex communication mode for performing multiplex transmission and a sleep mode in which the interface portion is kept inoperative, each node comprising: a reception circuit that is connected to the multiplex transmission path and receives from the other node via the transmission path a seizing signal for making a changeover of the operation mode from the sleep mode to the multiplex communication mode; a mode changing-over portion that changes over the operation mode from the sleep mode to the multiplex communication mode according to the seizing sig
Nakajima Katsutoshi
Nishiyama Hiroshi
Norizuki Akira
Saito Yoshikazu
Tomita Akiyoshi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Pham Brenda
Yazaki -Corporation
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