JPS63157543A - Address discriminating device - Google Patents

Abstract

PURPOSE:To prevent collision caused by the incoming of information frames during updating an address by preventing plural information frames from simultaneously flowing on a communication medium. CONSTITUTION:An address discriminating device 5 consists of an address memory 6 accumulating the address table to be transmitted and a control part 7 for changing the content of the address memory 6. The control part 7 has a function waiting until a transmitter-receiver transmits the information frames when the content of the address memory 6 needs to be changed, and changes the content o the address memory 6 simultaneously with transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an address discriminating device for determining whether an incoming information frame should be received in a communication device.

[Conventional technology]

A communication device has a function that looks at the destination address part of the information frame flowing on the communication medium to which the communication device is connected, and determines which information frames the device should accept and which information frames it does not need to accept. is necessary. In a normal communication device, the address of the own communication device is the only one fixedly given, and the information frame is received only when the destination address in the information frame is the address of the only own communication device.

However, in connection devices between communication networks, there are multiple addresses to be received, and these addresses may change dynamically during operation.

Conventionally, when there are multiple addresses to receive, the multiple addresses to be received are stored as a table in the reception memory, and once all information frames have been received in the reception memory, the CPU refers to the address table. The method used was to determine whether the message should have been received or not, and then discard it if it was not necessary to receive it.

Another possible method is to quickly determine the destination address of an incoming information frame before it is received in the reception memory, and if it is an information frame that does not need to be received, it is discarded before it is placed in the reception memory. This is the way to do it. From then on,
This method will be referred to as hardware filtering. Generally, the destination address is written at the beginning of the information frame, so if the address can be determined quickly enough, such a method is possible by providing a small buffer memory in front of the receiving memory.
[Problems to be Solved by the Invention] In the former method, information frames that do not need to be received are also temporarily received in the reception memory, which causes an overflow of the reception memory and imposes a heavy processing load on the CPU. There are drawbacks such as.

In the latter method, hardware filtering was possible when there was only one address to be discriminated, but hardware filtering was impossible when there were multiple addresses to discriminate because it took time to discriminate. Met. However, if you use a recently developed associative memory (content read memory) or special memory with a high-speed search function, you can perform sufficiently fast matching even when there are multiple addresses to receive, and receive information frames that do not need to be received. It becomes possible to make a determination without having to receive the data once into the memory. However, with this method, control when updating the contents of the address table poses a problem. That is, in hardware filtering, the destination address part of the information frame is directly input to the address discriminator, so it may be input during the updating of the routing table, and some kind of collision control for access by the address discriminator is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an address discrimination device that can avoid collisions caused by incoming information frames while updating an address table in hardware filtering.

[Means for solving problems]

The present invention is an address discrimination device for discriminating between information frames that should be received and information frames that do not need to be received in a communication device, and includes a memory that stores a table of addresses that should be received, and a memory that stores a table of addresses that should be received. When it is necessary to change the contents of the memory, the control section waits until its own communication device transmits an information frame and simultaneously changes the contents of the memory. It is characterized by doing.

[Effect]

Generally, in a communication network, multiple information frames do not flow at the same time on a communication medium connected to a single transmitting/receiving unit of a single communication device. information frame never comes in. Therefore, in the address determination device according to the invention, no other information frames come in during address updating, and it is ensured that no collisions occur.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an example of a transmitting/receiving device using the address discriminating device of the present invention. The address discrimination device 5 includes an address memory 6 that stores a table of addresses to be received, and a control section 7 for changing the contents of this address memory.The control section 7 changes the contents of the address memory 6. When necessary, it has a function of waiting until the transmitting/receiving device transmits the information frame and changing the contents of the address memory 6 at the same time as the transmission.

A transmitting/receiving device (communication device) 2 having such an address discriminating device 5 includes a transmitting/receiving interface 3, a transmitting/receiving control circuit 4, and a transmitting/receiving memory 8, and the transmitting/receiving control circuit 4 is a first-in/first-out type. It has Banfa.

The operation will be explained below. Information frames flowing on the communication medium 1 are input to the communication device 2 via the transmission/reception interface 3 . The input information frame passes through the transmitting/receiving interface 3 and is inputted to the transmitting/receiving control circuit 4, and only its address portion is inputted to the address memory 6 in the address discriminating device 5. A table of addresses to be determined is stored in the address memory 6,
If the address is not the one to be received, a discard signal is given to the transmission/reception control circuit 4. The transmission/reception control circuit 4 has a first-in/first-out type buffer, and there is a delay from input to output of an information frame. If no discard signal is input from the address memory 6, the transmission/reception control circuit 4 writes the input information frame to a predetermined address in the transmission/reception memory 8 with the delay time described above. When a discard signal is given, the information frame is transmitted and received by the memory 8.
Discard it without outputting it to the side.

Next, the operation when changing the contents of the address table in the address memory 6 will be explained with reference to the timing chart for changing the address table shown in FIG.

When a request to rewrite the address table of the address memory 6 is issued to the control section 7, the control section 7 waits for a transmission start signal from the transmission/reception control circuit 4 indicating the start of transmission of an information frame. When the transmission start signal is given, the control unit 7 starts rewriting the address table in the address memory 6, and ends the rewriting while the information frame is being transmitted. While an information frame is being transmitted, no other information frame comes in. Therefore, in the address discriminator 5, the address portion of another information frame does not come in while the address is being updated, and collisions occur. will not occur.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an address discriminating device that is guaranteed to prevent collisions due to incoming information frames while changing the table of addresses to be discriminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram explaining the present invention in detail, and FIG. 2 is a timing diagram when changing the address table. 1...Communication medium 2...Communication device 3...Transmission/reception interface 4...Transmission/reception control circuit 5...Address discrimination device 6...Address memory 7...Control unit 8...Transmission/reception memory

Claims (1)

[Claims] (1) An address discrimination device for discriminating between information frames that should be received and information frames that do not need to be received in a communication device, which includes a memory that stores a table of addresses that should be received, and changes the contents of this memory. The controller comprises a control unit for changing the contents of the memory, and the control unit waits until the own communication device transmits the information frame and changes the contents of the memory at the same time as the transmission. Features of address discrimination device.