JPH09102809A - Communication controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a communication protocol from being changed and to evade the omission of reception data from a computer network only by means of changing a small amount of hardware by transmitting collision data for permitting inputted data to be invalid to the network when held reception data quantity exceeds a threshold value. SOLUTION: Reception data from a host 110 is temporarily executed buffering in a reception FIFO 101. A reception FIFO monitoring part 102 normally monitors data quantity which is held by the reception FIFO 101 and outputs a signal indicating that quantity exceeds a previously set threshold value to a collision data transmitting part 103 at the time of exceeding the threshold value. The collision data transmitting part 103 transmits collision data to input data at the point of time when the signal is received from the reception FIFO monitoring part 102 at the time of reception. In result, a data collision occurs in the network and collided kinds of data are made to invalid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control device used in a computer network.

[0002]

2. Description of the Related Art Generally, a LAN (Local Area Network)
In such a terminal connected to a computer network, when a large amount of data is transmitted at one time, if the capacity of the reception data buffer is not so large, a large amount of data that cannot be captured will be generated. In addition, during data reception, when other operation other than communication is performed, the received data may be accumulated in the buffer, and it may not be possible to capture new data.

Therefore, conventionally, a large-capacity receiving buffer is provided to prevent data omission. In addition, Japanese Patent Laid-Open No. 1-2283
No. 53 and Japanese Patent Laid-Open No. 62-290224, the transfer clock between the transmitting side and the receiving side is made variable according to the situation to adjust the data transfer amount. As disclosed in No. 62-114346, there is an example in which, in the packet switching network, the packet length is changed on the transmitting side according to the capability of the receiving side so as to prevent data omission. .

[0004]

However, in the above-mentioned conventional techniques, the amount of hardware such as a large capacity buffer and a clock control unit is increased, and further software for constructing an original communication protocol is used. It is inevitable that the amount will increase. The present invention has been made in view of the current situation, without changing the communication protocol,
It is an object of the present invention to provide a communication control device capable of avoiding the loss of received data by only slightly changing the hardware.

[0005]

In order to achieve the above object, the present invention according to claim 1 holds a received data holding means for holding received data from a network, and a data held by the received data holding means. When the data amount monitoring means for monitoring whether the amount exceeds a predetermined threshold value and the data amount monitoring means confirms that the data amount held in the received data holding means exceeds the predetermined threshold value And a collision data transmission means for transmitting the collision data for invalidating the input data to the network.

According to a second aspect of the present invention, the received data holding means in the communication control apparatus according to the first aspect is
Further, it is characterized in that it comprises a data judging means for judging whether or not the received data should be held. Further, the invention according to claim 3 is such that when the received data holding means in the communication control device according to claim 2 judges that the received data is data to be held by the data judging means. The feature is that the data is held in the order of reception and the held data is output in the same order.

According to a fourth aspect of the present invention, the data amount monitoring means in the communication control device according to the first or third aspect further comprises a predetermined amount of data held in the received data holding means. If you confirm that the threshold is exceeded,
It is characterized by comprising collision data transmission instruction means for instructing the collision data transmission means to transmit the collision data.

Further, in the invention described in claim 5, the collision data transmission means in the communication control device according to claim 1 or 4 further receives an instruction from the collision data transmission instruction means. First communication mode switching means for switching from the data reception mode to the data transmission mode, and a second communication mode for switching from the data transmission mode to the data reception mode after transmitting the collision data. And a switching means.

Further, in the invention described in claim 6, the communication control device according to claim 1 or 5 further determines whether or not the network address of the received data matches the network address of the own station. And a network address determining means that determines that the network address of the received data matches the network address of the local station, and the data amount monitoring means holds the received data in the received data holding means. Second collision data transmission instruction means for instructing the collision data transmission means to transmit the collision data when it is confirmed that the amount exceeds a predetermined threshold value. It is characterized by being.

[0010]

According to the above construction, the data amount of the received data from the network held in the received data holding means is constantly monitored by the data amount monitoring means. And
When it is confirmed that the data amount exceeds the predetermined threshold value, the collision data transmission means transmits the predetermined collision data for the input data to the network. As a result, data collision occurs (that is, signals from one or more stations are on the bus at the same time) on the network, and the collided data are both invalidated. Therefore, the data transmitting side retransmits the same data, and the receiving side waits for reception of the retransmitted data. In the meantime, the received data holding means recovers its holding ability, so that data loss is avoided here.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a first embodiment of a communication control device according to the present invention. As shown in the figure, here, the host 110 and the terminal 111 are connected via the network 100 and the communication interfaces a and b.

The communication control device is provided in the terminal 111 and is configured to transmit and receive data to and from the host 110 via the network 100. The reception FIFO 101 and the reception FIFO monitoring unit 102 are provided. A collision data transmission unit 103, a transmission FIFO 104,
A driver / receiver 105, a data processing unit 106,
The communication interface a is provided. Then, the data processing unit 106 exchanges transmission / reception data with the central control unit 107 that controls the entire terminal 111.

As the network 100, for example, Ethernet (Ethern) which is a bus type LAN in which both ends are terminated with a characteristic impedance and each terminal is wired in a branch shape is used.
et) is used. Ethernet is a transmission speed of 10M created by IEEE (Institute of Electrical and Electronics Engineers) 802.3.
Although it is a LAN of bps, more specifically, depending on the type of cable used, 10BASE5 (however, the number 10
Has a transmission speed of 10 Mbps, BASE is baseband transmission, and numeral 5 after BASE has a transmission distance of 5
00m) and 10BAS
There are variations such as E2 (however, the numeral 2 indicates that the transmission distance is 200 m) and 10BASE-T (however, T indicates that a twisted pair is used). Recently, high-speed Ethernet with a transmission speed of 100 Mbps has also appeared.

In the reception FIFO 101, the host 110
Temporary buffering of received data from. In the reception FIFO monitoring unit 102, the reception FIFO
The amount of data held in O101 is constantly monitored, and when a predetermined threshold value is exceeded, a signal to that effect is output to the collision data transmission unit 103.
Then, in the collision data sending unit 103, the reception FIF
When the signal from the O monitoring unit 102 is received, the collision data is transmitted to the input data at that time. Further, in the normal case, the transmission FIFO 104 temporarily buffers the transmission data from the data processing unit 106.

FIFO (First In First Out Memory)
Is a memory that is configured to be read sequentially from the first written data, and because the data input / output order is maintained, it is used for the purpose of speed difference absorption in data transfer between devices with different operating speeds. To be done. In this embodiment, for example, a FIFO with a capacity of 64 KB is used.
The driver / receiver 105 receives data from the network 100 and transmits data to the network 100 through the communication interface a. When Ethernet is used as the network 100, CSMA / CD (Carrier sense multiple)
access with collision detection) method, when the transmission with another terminal wins, the data is transmitted after waiting a random time. , The data transmission is prioritized.

In the data processing unit 106, the network 1
The data received from 00 is processed and sent to the central control unit 107, and conversely, should be transmitted to the network.
Process the data from 7. Further, the central control unit 107 exchanges data with the data processing unit 106 and controls the entire terminal 111. FIG. 2 is a schematic diagram showing the structure of a general packet used in Ethernet. In Ethernet, data is handled in packet units and the packets are transmitted and received. As shown in the figure, one packet is composed of a header (control information that is added at the beginning of the packet and is necessary for transmission), and subsequent transmission data of up to 1.5 KB. . The header is a destination address represented by 6 bytes, a source address (also called a MAC address) which is also represented by 6 bytes, and a packet length which is further represented by a variable length (here, 2 Byte) data.

FIG. 3 is a flow chart showing the control operation of the communication control device shown in FIG. 1 when receiving data.
When data reception is started through the driver / receiver 105 (Yes in S1), the reception FIF
The O monitoring unit 102 monitors whether or not the amount of data in the reception FIFO 101 exceeds a preset threshold (S2). The receiving FIFO
In 101, the received data is for the own station or for all terminals.

When it is confirmed that the threshold of the receiving FIFO 101 is exceeded (Y in S2)
In the case of es), the transmission enable signal is output to the collision data transmission unit 103 (S3). Further, the collision data transmission unit 103 that has received the transmission enable signal switches the communication mode from the reception mode to the transmission mode and uses the collision data prepared in advance in the driver / driver.
Output to the receiver 105. Then, the driver operates to send the collision data to the network 10 via the communication interface a (S4). As a result,
On the network 100, the transmitted collision data and the input data collide with each other and both of them are invalidated.

Then, the host 110 side, which has detected that the transmission data has become invalid, retransmits the invalid data. Further, the collision data transmission unit 103 on the terminal 111 side immediately switches the communication mode from the transmission mode to the reception mode after transmitting the collision data.
Wait for new data after the collision. At this time, the reception FIFO 101 is returned to a state in which the data does not overflow and the data is not lost.

When the data amount of the receiving FIFO 101 does not exceed the threshold (N in S2)
If it is o), confirm whether to end the reception (S
5) If the reception is not ended (No in S5), the process proceeds to step S2 and the reception FIFO is used.
When the monitoring of the data amount in O101 is continued and the reception is ended (Yes in S5), the reception process is ended.

Since the purpose of the collision data is to cause a data collision in order to invalidate an input packet, the data content may be meaningless, for example, , A packet of an arbitrary length is used in which all the destination address portions are at the "+" level. FIG. 4 is a block diagram showing the configuration of the second embodiment of the communication control device according to the present invention. As shown in the figure, here, the host 210 and the terminal 2 are connected via the network 200 and the communication interfaces a and b.
11 and the terminal 212 are connected to each other.

This communication control device is also provided in the terminal as in the case of the above-described first embodiment, and its configuration is approximately the same as that of the communication control device shown in FIG.
That is, the reception FIFO 201, the reception FIFO monitoring unit 202, the collision data transmission unit 203, and the transmission FIFO.
An O204, a driver / receiver 205, and a data processing unit 206 are provided, but in addition to this, an address determination unit 208 is newly added. In the data processing unit 206, transmission / reception data is exchanged with the central control unit 207.

When the address determination section 208 extracts the destination address section from the data being received and confirms that it matches the Ethernet address of itself, it outputs a signal indicating that to the collision data. Output to the sending unit 203. Then, in the collision data transmission unit 203, the reception FIFO monitoring unit 202 and the address determination unit 2
The collision data is transmitted only when both of the signals from 08 are received.

FIG. 5 is a flowchart showing the control operation of the communication control device shown in FIG. 4 when receiving data.
When data reception is started through the driver / receiver 205 (Yes in S11), the address determination unit 208 confirms whether or not the input data is for itself (S12). When it is confirmed that the data is addressed to itself (Yes in S12), the transmission enable signal Y is output to the collision data transmission unit 203 (S13), and the process proceeds to step S16. To do.

If it is confirmed that the data is not addressed to itself (No in S12), step S
The processing shifts to 11. In this case, since the transmission enable signal Y is not output to the collision data transmission unit 203, even if the data amount in the reception FIFO 201 exceeds the preset threshold, the collision data may be transmitted. In addition, it does not destroy the transmission data to other terminals.

Further, in the reception FIFO monitoring section 202,
It is monitored whether the amount of data in the reception FIFO 201 exceeds a preset threshold (S1).
4). When it is confirmed that the data amount of the reception FIFO 201 exceeds the threshold (Yes in S14), the transmission enable signal X is output to the collision data transmission unit 203 (S15). ,
The process moves to step S16.

In the collision data transmission unit 203, it is confirmed whether or not both the transmission enable signals X and Y are output (S16), and when both signals are output (Yes in S16). Only, the collision data is output to the driver / receiver 105 (S1
7). As a result, the collision data is transmitted to the network 200 through the communication interface a, the collision of the transmitted collision data and the input data occurs on the network 200, and both of them are invalidated.
Therefore, the host 210, which has detected that the transmission data has become invalid, retransmits the invalid data. Further, in the terminal 211 (or the terminal 212), the reception FIFO 201 has returned to a state in which data loss does not occur, and new data after collision can be received.

When the threshold of the reception FIFO 201 is not exceeded (No in S14), it is confirmed whether or not the data reception is to be ended (S18), and the data reception is not to be ended. In the case of (No in S18), the process proceeds to step S14, the monitoring of the data amount in the reception FIFO 201 is continued, and when the reception of the data is finished (Yes in S18), the reception process is performed. To finish.

In the first embodiment described above, only one host 110 is connected to the network 100.
In the second embodiment, one host 210 is connected to the network 200 and terminals 211 and 212 are connected to the network 200 in the second embodiment.
However, it goes without saying that the number of hosts and the number of terminals may be increased as long as the network 100 or 200 permits.

[0030]

According to the communication control device of the present invention,
On the side of the terminal connected to the network, the amount of received data held in the FIFO is constantly monitored, and when the amount of data exceeds a certain amount, the data for collision prepared in advance is output to determine whether the data is being received or , The data to be newly received is supposed to collide. On the other hand, the transmitting side confirms that the transmitted data has been invalidated due to the data collision, and retransmits the invalidated data. During this time, the data holding capability of the FIFO is restored on the terminal side, so that the data retransmitted subsequently is received.

As described above, on the terminal side, it is possible to easily avoid the loss of received data by only changing the minimum amount of hardware without changing the conventional communication protocol. become. In addition, it is configured to output the collision data only when it is confirmed that the data is addressed to itself and when it is confirmed that the data holding amount of the FIFO exceeds a certain amount. It is possible to reliably prevent the occurrence of the problem that the collision data destroys the data for other terminals.

Therefore, if this communication control device is used, even if the data receiving capability on the terminal side is low, data can be reliably received without causing data zeroing. In the data communication system, the terminal function can be fully exerted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a communication control device according to the present invention.

FIG. 2 is a schematic diagram showing a configuration of a general packet used in Ethernet.

FIG. 3 is a flowchart showing a control operation of the communication control device shown in FIG. 1 when receiving data.

FIG. 4 is a block diagram showing a configuration of a second embodiment of the communication control device according to the present invention.

5 is a flowchart showing a control operation of the communication control device shown in FIG. 4 when receiving data.

[Explanation of symbols]

 100, 200 network 101, 201 reception FIFO 102, 202 reception FIFO monitoring unit 103, 203 collision data transmission unit 104, 204 transmission FIFO 105, 205 driver / receiver 106, 206 data processing unit 107, 207 central control unit 110, 210 Host 111, 211, 212 Terminal a, b Communication interface X, Y Send enable signal

Claims (6)

[Claims] 1. A reception data holding means for holding reception data from a network, a data amount monitoring means for monitoring whether or not the data amount held by the reception data holding means exceeds a predetermined threshold value, and the data amount. When it is confirmed by the monitoring means that the amount of data held in the received data holding means exceeds a predetermined threshold value, collision data for invalidating the input data is sent to the network. A communication control device comprising: collision data transmission means; 2. The communication control device according to claim 1, wherein the reception data holding means further comprises a data judgment means for judging whether or not the reception data should be held. 3. The received data holding means holds the data in the order of reception when the data judging means judges that the received data is data to be held, and holds the held data. The communication control device according to claim 2, wherein the communication control devices output the data in the same order. 4. The data amount monitoring means further determines whether or not the collision data transmission means is to be used for collision when it is confirmed that the data amount held in the reception data holding means exceeds a predetermined threshold value. The communication control apparatus according to claim 1 or 3, further comprising: collision data transmission instruction means for instructing to transmit data. 5. The first communication mode switching means for switching the data reception mode to the data transmission mode when the collision data transmission means further receives an instruction from the collision data transmission instruction means. 5. A communication means for switching from a data transmission mode to a data reception mode after transmitting the collision data, and a second communication mode switching means. Communication control device. 6. The communication control device according to claim 1 or 5, further comprising: a network address determining means for determining whether or not the network address of the received data matches the network address of the local station. The network address determination means determines that the network address of the received data matches the network address of the own station, and the data amount monitoring means causes the amount of data held in the received data holding means to exceed a predetermined threshold value. When it is confirmed, the communication control is characterized by further comprising: second collision data transmission instruction means for instructing the collision data transmission means to transmit the collision data. apparatus.