JPH07107101A - Communication controller - Google Patents

Abstract

PURPOSE:To realize the communication controller by which a definite access of each communication station is secured, ans all the communication stations can use equally a circuit even in the case a load on the circuit is high. CONSTITUTION:A transmitting station instructing means 22 of a master station sends out a transmitting station instruction frame containing bit mask information and transmission permitting station address information, while updating the bit mask information and the transmission permitting station address information at every prescribed period. A transmission station recognizing means 23 of all the communication stations containing the master station receives the transmitting station instruction frame sent out of the transmitting station insulating means 22. Subsequently, AND of the bit mask information contained in the received frame and a station address of the own station is taken, and this AND and the transmission permitting station address information contained in the tramsmitting station instruction frame are compared, and in the case a result of comparison coincides, the transmission is permitted to a transmitting/ receiving means 21 of the own station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a LAN (Local).
Connect multiple communication stations to Area Network),
CSMA / CD system (Carrier) between each communication station
SenseMultiple Access / Coll
The present invention relates to a communication control device applied to a communication system that performs communication according to the (ion Detection method). More specifically, it relates to a communication control device devised so that each communication station can make definite access to a LAN line.

[0002]

2. Description of the Related Art There is a CSMA / CD system as a media access system in a LAN.
Used in THERNET. In the CSMA / CD system communication, there is no master-slave relationship between the master station and the slave station as in the polling / selection system communication, and each communication station can freely access if the line is unused. Further, when a plurality of stations access at the same time and a collision occurs, the communication procedure is such that the access is tried again by a stochastic algorithm. However, in the communication of the CSMA / CD system, not only the access of each communication station is not definitely guaranteed, but especially when the load on the line is high, only the access probability of a specific communication station is greatly reduced. There was a drawback that it would end up. here,
The case where the load on the line is high is the case where there are many communication stations that want to transmit to the line.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks, and a master station is defined, and a communication station that can use a line is specified from this master station. Guarantees definite access of
An object of the present invention is to realize a communication control device in which all communication stations can use the line equally even if the load on the line is high.

[0004]

The present invention is applied to a communication system in which a plurality of communication stations are connected to a LAN and communication is performed between the communication stations by the CSMA / CD system, and the communication provided in each communication station. In the control device, transmission / reception means for performing transmission / reception with the LAN, bit mask information for operating only when the own station becomes the master station, and specifying the specific bit in the station address of the communication station, and transmission. A transmission station instruction frame including transmission permission station address information for designating the station address of the communication station to be permitted by the specific bit portion designated by the bit mask information is transmitted to the LAN via the transmission / reception means, and this transmission station instruction is issued. In the frame, the transmission station instruction means for transmitting while updating the bit mask information and the transmission permission station address information at regular intervals, and the transmission station instruction frame transmitted by this transmission station instruction means. Received, the logical product of the bit mask information contained in the received frame and the station address of the local station is calculated, and this logical product is compared with the transmission permission station address information contained in the transmission station instruction frame. The communication control device is provided with a transmitting station recognizing unit that permits the transmitting and receiving unit of the own station to transmit when they match.

[0005]

According to the present invention, the transmitting station designating means of the master station sends the transmitting station designating frame containing the bit mask information and the transmission permitting station address information to the bit mask information and the transmission permitting station address information at regular intervals. Send while updating. The transmitting station recognizing means of all communication stations including the master station receives the transmitting station instruction frame transmitted by the transmitting station instruction means.
Then, the logical product of the bit mask information contained in the received frame and the station address of its own station is calculated, and this logical product is compared with the transmission-permitted station address information contained in the transmitting station instruction frame, and the comparison results are in agreement. In this case, the transmission / reception means of the own station is permitted to transmit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Figure 1
FIG. 1 is a schematic configuration diagram of a communication system to which the present invention is applied. In FIG. 1, L is a communication medium using a LAN, S1 to S8
Is a communication station connected to the communication medium L. Communication station S1
Station addresses 1 to 8 are assigned to S8 in the order of arrangement. The station address is given as 1-byte data, for example.

FIG. 2 is a block diagram of an embodiment of the present invention.
2 that are the same as those in FIG. 1 are given the same reference numerals. In Figure 2,
Reference numeral 1 is a communication station such as S1 to S8 in FIG. 1, and 2 is a communication control device according to the present invention provided in the communication station 1. In the communication control device 2, reference numeral 21 is a transmitting / receiving means for transmitting / receiving to / from the communication medium L. Reference numeral 22 is a transmitting station instruction means that operates only when the own station is a master station. In the transmitting station instruction means 22, reference numeral 221 is a memory which stores bit mask information and transmission permitted station address information. The bit mask information is information that specifies a specific bit in the station address of the communication station. The information on the authorized station address is
This is information that specifies the station address of the communication station whose transmission is permitted by the specific bit portion specified by the bit mask information. Two
22 is a sending means for sending a transmitting station instruction frame containing bit mask information and transmission permitting station address information to the communication medium L via the transmitting and receiving means 21 at a constant cycle, and 223 is updating bit mask information and transmission permitting station address information. It is an updating means to perform. Reference numeral 23 is a transmitting station recognizing means. In the transmitting station recognizing means 23, reference numeral 231 is a logical product circuit for taking the logical product of the bit mask information included in the transmitting station instruction frame received by the own station and the station address of the own station, and 232 is the logical product circuit 231. The comparison means 233 for comparing the logical product with the transmission permitted station address information included in the transmission station instruction frame received by the own station, and the comparison means 233, when the comparison result of the comparison means 232 is the same, transmits to the transmission / reception means 21 of the own station. It is a permission means to permit. The station address is stored in the memory of the communication station, for example.

The operation of the communication control device thus configured will be described. In the communication system of FIG. 1, the communication station S1 is a master station. The communication station S1 transmits a transmission station instruction frame to each communication station by the transmission station instruction means 22 of its own station.
That is, for example, the bit mask information is set to “0011”,
A transmission station instruction frame is formed by setting the transmission permission station address information to "0001", and the transmission / reception means 21 communicates with the communication medium L.
Send the frame to. The bit mask information and the transmission permission station address information are binary numbers. Each communication station that has received the transmission station instruction frame from the communication medium L has the transmission station recognition means 23.
The logical product of the bit mask information “0011” and the station address of the own station is calculated by using, and the obtained logical product is compared with the value of the transmission-permitted station address information “0001”. If the comparison result matches, transmission / reception of the own station Permit transmission to the means 21. In the case of this example, the communication station whose lower 2 bits of the station address is “01”, that is, the communication station S1 (station address “0001”)
And S5 (station address "0101") are permitted to be transmitted. After a lapse of a certain time, the communication station S1 increases the transmission-permitted station address information by 1 by the transmission station instruction means 22,
The transmitting station instruction frame is sent again as "0010". As a result, the communication stations S2 (station address "0010") and S6 (station address "0110") are permitted to transmit by the same operation as described above. By repeating the above procedure, the master station S1 obtains the transmission-permitted station address information at a constant cycle: 0001 → 0010 → 0011 → 0000 → 0001 →
The transmitting station instruction frame is transmitted while being updated as follows.
By this operation, the transmission right is sequentially given to each communication station.

[0009]

According to the present invention, it is possible to prevent a communication station on a line from accessing the communication station at one time by indicating from the master station which communication station can use the line. This guarantees deterministic access of each communication station, and suppresses the collision on the line that is characteristic of CSMA / CD communication within a certain range even when the line is under heavy load, and all communication The stations can use the lines equally.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a communication system to which the present invention is applied.

FIG. 2 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 S1 to S8, 1 communication station L communication medium 2 communication control device 21 transmission / reception means 22 transmission station instruction means 23 transmission station recognition means

Claims (1)

[Claims] 1. A communication control device provided in each communication station, which is applied to a communication system in which a plurality of communication stations are connected to a LAN and performs communication by the CSMA / CD system between the communication stations. The transmission / reception means that performs transmission / reception with, the bit mask information that operates only when the local station becomes the master station, and specifies the specific bits in the station address of the communication station, and the station address of the communication station that permits transmission. A transmission station instruction frame including the transmission permitted station address information designated by the specific bit portion designated by the bit mask information is transmitted to the LAN via the transmission / reception means, and the transmission station instruction frame has the bits at regular intervals. A transmitting station instruction means for transmitting while updating the mask information and the transmission permission station address information, and a frame for receiving the transmitting station instruction frame transmitted by this transmitting station instruction means. The logical product of the bit mask information contained in the program and the station address of its own station is compared, and this logical product is compared with the transmission-permitted station address information contained in the transmitting station instruction frame. A communication control device, comprising: a transmitting station recognizing unit that permits transmission to a transmitting / receiving unit of the station.