JPS62204640A - Data communication system - Google Patents

Abstract

PURPOSE:To speed up the invitation of transmission by using the 2-division retrieval method to retrieve a subsequent station having a transmission request. CONSTITUTION:A control station CST divides subsequent stations ST1-STm into two groups and applies the sending invitation to one group. Since a subsequent station STi having a transmission request output the transmission request, the control station CST regards it as the absence of the transmission request in the group not applying the transmission invitation when no transmission request signal is received and repeats the 2-division transmission invitation of the group again to the group of the subsequent stations having the transmission request.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a data communication system that follows a polling/selecting transmission control procedure, and particularly relates to a data communication system using a polling method that allows high-speed transmission solicitation even when there are a large number of terminals. Regarding communication systems.

[Background of the invention]

As a method of increasing the speed of polling in a data communication system that follows the conventional polling/selecting transmission control procedure, for example, as shown in Japanese Patent Laid-Open No. 160351/1982, a method for increasing the speed of polling is to A method of increasing data transmission efficiency by polling and selecting is known.

However, this method is applicable only when the dependent stations are connected to the control station through independent transmission lines, and cannot be applied to a bus type network. Further, this method has problems such as its purpose being to increase data transmission efficiency, and not to reduce the amount of data transmitted in polling/selecting itself.

(Object of the Invention) An object of the present invention is to provide a polling-type data communication system that can perform a transmission invitation to a dependent station that has a transmission request at high speed by searching for a dependent station that has a transmission request using a binary search method. It is about providing.

[Summary of the invention]

The present invention provides a data communication system according to a polling/selecting transmission control procedure, in which a transmission request circuit is provided for outputting a transmission request signal to a dependent station, and a transmission request detection circuit is provided for a control station to detect the transmission request. The station divides the dependent stations into two groups and invites one group to transmit, and among the dependent stations that receive the invitation, the dependent station that has a transmission request outputs the transmission request signal, so the control is performed. When a station receives a transmission request signal as a result of a transmission invitation, it assumes that there is a dependent station with a transmission request in the group that conducted the transmission invitation, and does not conduct a transmission invitation when it does not receive a transmission request signal. The control station assumes that there is a dependent station with a transmission request in the group, and repeats the operation of splitting the group into two and inviting transmission to the group in which the dependent station with a transmission request exists. This is a polling-based data communication system that can quickly search for a dependent station that has a transmission request from among the dependent stations in the form of a binary search.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

The first factor is a block diagram of a connection method showing an embodiment of a data communication system according to the present invention.

In the figure, C5T is a control station, ST1 to ST5rnt are dependent stations, and these control stations and each dependent station share a common line fq,
They are connected in parallel by CL.

FIG. 2 is a block diagram showing the configuration of an arbitrary dependent station STi in FIG. 1. In the same figure, RX-1 is connected to the common line CL
T X -i is a data transmitting circuit that outputs data onto the common line CL;
C-1 is a control circuit, and PT-i is a transmission request signal output circuit that outputs a transmission request signal onto the common line.

FIG. 3 is a block diagram showing the configuration of control station C5T in FIG. 1. In the figure, RX is a data receiving circuit, rx is a data transmitting circuit, CC is a control circuit, and PR is a transmission request detection circuit that detects that a transmission request signal is output on the common line and notifies the control circuit CC. be.

Here, for example, 256 dependent stations ST1 to 5TrpL are connected, and addresses are assigned to these using 8-bit binary codes, and the control station csr uses this address to solicit group transmissions. Next, as an example of the operation of the data communication system according to the present invention, the operation until the dependent station ST-like obtains the transmission right through a transmission invitation will be explained.

First, in the control station csr, the control circuit CC is connected to the common line (
, L becomes vacant, the data transmission circuit TX is used to invite transmission. This invitation is sent to any slave station ST
i is detected by the data receiving circuit RX-i and notified to its control circuit CC-1. This transmission invitation is for a group of dependent stations, and in addition to the address, a code specifying the significant digits of the address is added. The first invitation sent by the control station csr has an address in binary code (0
0000000)B, and the leading digit is the upper 1 bit. This indicates that a request is being made to a dependent station whose address has a 0 in the upper 1 bit, and all dependent stations are sent to addresses below (Ollllllll)B and (10000).
000)a It is divided into two parts, and one of them is (011
11111) This means that a transmission invitation is being made to dependent station groups below B. For example, assume that the only dependent station that currently has a transmission request is S T m, and that the hidden address of dependent station sr is (10001100)a.

When the control port Bcc- of this dependent station STm receives the invitation, it compares the addresses using only the high-order bit, which is a trailing digit, and since they do not match, it knows that the invitation is for another group. , does not output a transmission request signal. In addition, other dependent stations do not output transmission request signals because they do not have transmission requests regardless of their addresses.

Therefore, since the control circuit CC of the control station csr that made the transmission invitation does not detect the transmission request signal, it means that there is no dependent station that has a transmission request among the dependent stations whose address has the upper 1 bit of 0. Among the dependent station groups previously divided into two, the address is (01111111)a
It is known that there are no dependent stations with transmission requests in the following groups. As a result, the control circuit c of the control station csr
C thinks that there is a dependent station with a transmission request in a group of dependent stations with addresses of (10000000)5 or more, and changes the most significant bit of the address of the invitation to send from O to 1, making it (10000000)B, and controls. The second invitation sent by station CSR has the address (10000
000) # (!: and the significant digits are the upper 2 bits. This indicates that a transmission invitation is being made to a dependent station whose upper 2 bits of the address are 10, and the address is (1
0000000)a A group of subordinate stations above and below address (10111111)J and below (110
00000) II It is divided into two parts, and one of them is (
10111111)B means that the following dependent station groups are invited to send. Dependent station 5Tr
When rr receives the second invitation to send, it compares the addresses using only the most significant two bits. This subordinate station S
As mentioned above, the address of T m is (10001100)
Since the addresses match, the control circuit CC-m knows that the transmission invitation is for the group to which it belongs, and outputs a transmission request signal onto the common line CL via the transmission request circuit. do.

This transmission request signal is transmitted to the transmission request detection circuit P of the control station csr.
R is detected and transmitted to its control circuit CC. Therefore, the control circuit CC of the control station csr recognizes that there is a dependent station with a transmission request among the dependent stations whose address has the upper 2 bits of 10, or in other words, the previously divided address is (10000000)B or more. Among the station groups, the address is (10111111)B or less, that is, the address is from (xoooooooo)a to (
10111111) Considering that there is a dependent station with a transmission request in the group up to B, the second most significant bit of the transmission invitation address is not changed, and the third transmission invitation sent by the control station csr is is the address (100000
00)fl, and the significant digits are the upper 3 bits. As can be seen from the above process, the series of operations from the invitation to send is nothing but comparing and modifying the address set by the control station csr for each bit.

Therefore, by repeating the invitation for transmission eight times in the same manner, the control station csr will always receive the dependent station ST that has a transmission request.
You can know the address of m. According to this example:
The 8th transmission invitation sent by the control station csr is address (10001100)B, and the most significant digits are the upper 8 bits, that is, all digits are valid, and the address is similar to the transmission invitation in the normal polling/selecting transmission control procedure. The designated dependent station 5TrI& can obtain the transmission information. Suppose that the address of dependent station S T m is (100011
01)j, the eighth invitation to send is address (looolloo)B, and the significant digits are the upper 8 bits, but since there is no response to this invitation, the least significant bit is omitted. Change from to 1 and add the address (
10001101)B If the transmission invitation is performed with the significant digits as the upper 8 bits, the transmission right can be given to the dependent station S T m.

As described above, in a data communication system where a plurality of N dependent stations are connected, in order to grant the transmission right to a dependent station that has a transmission request, the conventional method using the polling/selecting transmission control procedure requires a maximum of N times. In contrast, the method according to the present invention requires invitations to send Lo , q t
/'/ + Transmission rights can always be granted with a single invitation.

〔Effect of the invention〕

According to the present invention, dependent stations are divided into groups and polling operations are performed, and the group is changed and the range of the group is reduced in response to a transmission request signal from the group. Since the inefficiency of searching can be resolved and transmission invitations can be made to dependent stations having transmission requests at high speed, the overhead of data communication in the polling method can be greatly reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a connection system showing an embodiment of the data communication system according to the present invention, FIG. 2 is a block diagram showing the configuration of an arbitrary dependent station STi in FIG. 1, and FIG. FIG. 3 is a block diagram showing the configuration of a control station C5T. CL...Common line csr...Control station ST1
to S T m...Subordinate station RX-i, RX...Data receiving circuit TX-i, i'X...Data transmitting circuit FT-i...
Transmission request circuit PR...transmission request detection circuit.

Claims (1)

[Claims] A plurality of dependent stations are connected to a single control station by independent or common transmission lines, and the control station invites each of the dependent stations to transmit, thereby transmitting information between the dependent stations or between the control station and each dependent station. In a data communication system according to a polling/selecting transmission control procedure in which data communication is performed at
A transmission request detection circuit is provided for detecting an output from one dependent station, and the control station polls the dependent stations in groups, and each dependent station having a transmission request polls the group to which it belongs. When the request is made, the transmission request circuit outputs a transmission request signal, and the control station detects that the transmission request signal is output from a dependent station by the transmission request detection circuit, and changes the group of dependent stations. A polling type data communication system characterized in that by reducing the range of a group, transmission invitations to dependent stations having a transmission request are performed at high speed.