Multiplex communications – Channel assignment techniques – Details of circuit or interface for connecting user to the...
Reexamination Certificate
1998-03-06
2002-02-19
Vu, Huy D. (Department: 2739)
Multiplex communications
Channel assignment techniques
Details of circuit or interface for connecting user to the...
C370S522000
Reexamination Certificate
active
06349102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data transmission method by polling and a terminal apparatus for use in the method. In particular, it relates to a method and a terminal apparatus in which an identifier (ID) of the terminal apparatus for polling can be changed easily.
In recent years, data transmission systems, in which a plurality of terminal apparatuses are connected with a host apparatus to execute a data transmission between them, have been widely used. In these transmission systems, a plurality of terminal apparatuses are connected simultaneously to a communication line, and data transmission is carried out by a host apparatus conducting polling of a corresponding terminal apparatus.
2. Description of the Related Art
Data transmission in a conventional method using the data transmission systems mentioned above has been carried out, in general, as described below.
The host apparatus conducts polling of the respective terminal apparatuses using their respective IDs by asking if they have data to be transmitted to the host apparatus. Each terminal apparatus monitors the line for its own ID. If a terminal apparatus having data to be transmitted to the host apparatus detects its own ID, it forwards a communication request to the host apparatus. Thus, communication between the host apparatus and the terminal apparatus is established to transmit data.
Identification information (identifier, referred to as an ID below) is unique to the respective terminal apparatus and is registered by the host apparatus at an initial stage of the data transmission procedure.
Since IDs in a conventional system have been uniquely given to the respective terminal apparatus, as mentioned above, the following problems have arisen.
For example, when a system as described above is constructed, new IDs should be determined for the respective terminal apparatus which will be connected to a host apparatus of the system. In addition, the newly determined IDs of the respective terminal apparatus should be registered to the host apparatus. These procedures to determine and register the respective IDs of the terminal apparatus in the data transmission system are not easy and require the efforts of a system engineer. In addition, when introducing more terminal apparatuses to the system later, the same procedures mentioned above should be repeated to determine and register the IDs of the new terminal apparatuses.
Further, since terminal apparatuses incorporated in the system sometimes break down, the broken ones must be replaced. Thus, the determination and registration of IDs mentioned above should be carried out again for the replaced apparatuses. If an ID which is different from that of the broken apparatus is determined at the replacement, ID management for the system becomes complicated, thus increasing the burden on a system engineer.
As explained above, by uniquely and fixedly determining an ID for each terminal apparatus, the time required for ID management increases and a large effort is necessary to re-establish new IDs in the data transmission system.
SUMMARY OF THE INVENTION
The present invention was made to overcome the above mentioned problems of the prior art. Therefore, the object of the present invention is to provide a data transmission method whose ID management is easier than a conventional method and which is able to omit a reestablishing procedure of a new ID when a terminal apparatus is replaced with a new one.
Another object of the present invention is to provide a terminal device which is suitable for use in the data transmission method of the present invention.
In order to achieve the above-mentioned object, the present invention provides a data transmission method for transmitting data in a system having a host apparatus (host station) and at least one terminal apparatus (terminal station) connected to the host apparatus. In this method, first, the host apparatus forwards a transmission request to the terminal apparatus. Then, corresponding to this transmission request, the terminal apparatus sends back a communication request to the host apparatus. In this communication request, a timer value of a system timer, which is incorporated in the terminal apparatus, is included. Having received the communication request including the timer value, the host apparatus establishes an ID for the terminal apparatus according to the timer value. Then, the host apparatus conducts polling for collecting data from the terminal apparatus using the established ID.
According to the above feature, the method of the present invention does not require fixed determination of an ID of the terminal apparatus, thus overcoming the problems of the prior art methods mentioned previously. In recent years, particularly, devices used to construct terminal apparatuses usually contain a system timer, and therefore, little effort is required to construct a terminal apparatus which can be used with the data transmission method of the present invention.
In another feature of the present invention, the host apparatus compares timer values of respective terminal apparatuses when the system includes a plurality of terminal apparatus and some of them forward communication requests simultaneously in response to a transmission request sent by the host apparatus. Then, the host apparatus gives a priority to one of the terminal apparatuses according to the compared result and establishes an ID for the terminal apparatus having a priority according to its timer value.
Due to the above feature, the present invention is able to give the priority to one of the terminal apparatuses by a very easy procedure. Therefore, the host apparatus is not required to keep information regarding which terminal apparatus has priority and other information regarding the priority sequence among a plurality of terminal apparatuses. Accordingly, the present invention can flexibly deal with the replacement of a terminal apparatus or addition of more terminal apparatus in a data transmission system.
In still another feature of the present invention, the timer value itself is established as the ID.
In still another feature of the present invention, a terminal apparatus is provided which is suitable for use with the transmission methods mentioned above. This terminal apparatus comprises a timer for counting time intervals, a memory for storing a value of said timer when the terminal apparatus can communicate with the host apparatus, and a controller for forwarding a reply to a transmission request which is received from the host apparatus, said controller incorporating said timer value into a reply and forwarding it to the host apparatus.
In still another feature of the present invention, a further terminal apparatus is provided which is suitable for use with the data transmission methods mentioned above. This terminal apparatus is comprised of a communication adapter connected with the host apparatus through a communication line and a portable terminal which is connectable with the host apparatus through said communication adapter, said portable terminal including, a timer for counting time intervals, a memory for storing a value in said timer when the terminal apparatus can communicate, and a controller for forwarding a reply to a transmission request which is received from the host apparatus, said controller incorporating said timer value into the reply and forwarding it to the host apparatus through said communication adapter.
In still another feature of the present invention, a host apparatus is provided which is suitable for use with the data transmission methods mentioned above. This host apparatus is comprised of a communication controller for forwarding a transmission request to said terminal apparatus and for receiving from said terminal apparatus a reply corresponding to the transmission request, an identification information establishing unit for extracting a timer value obtained from a timer contained in said terminal apparatus from the reply, which is received from the terminal apparatu
Murata Akio
Shibasaki Tomoki
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Vu Huy D.
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