JP2000324199A - Duplex communication circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a duplex communication circuit which quickly performs system switching to a LAP-B circuit for a preliminary system and also performs switching without interrupting LAP9-B protocol communication when a LAP-B circuit for the current operation system fails in a duplex communication system which has 1st and 2nd LAP-B circuits for one LAP-B communication line. SOLUTION: This circuit is provided with protocol controllers 73 and 83 which manages the control of a receiving function and a transmitting function and a LAP-B protocol, a communication management controller 40 having a register holding the preceding LAP-B protocol state and a transmission switching part 30 which selects a transmission signal to a transmission communication line 20 and transmission signals from two CCEs (protocol communication controller) 70 and 80 according to an instruction of the controller 40 inside the CCEs 70 and 80, and the controller part 40 parallelly operates the two CCEs 70 and 80, compares and monitors the states of the two CCEs 70 and 80 to detect a fault and has a function that selects a CCE accessing a receiving buffer and a function selecting a transmission signal to the line 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a duplex communication circuit,
Especially LAP-B (Link Access Procedure Balanced)
Mode = balanced link access procedure protocol).

[0002]

2. Description of the Related Art This kind of prior art is disclosed in, for example,
No. 2,169,971. As shown in FIG. 2, the duplex communication circuit includes a pair of protocol communication control devices (hereinafter, CCE) 110 and 120 connected to one communication line 100 via a switch 101. Each CCE 110, 120 has a LAP-B 111, 1
21, a processing unit (hereinafter, referred to as a PRC) 11 that controls a layer 3 or higher protocol in addition to controlling these LAP-Bs
2 and 122 and bus control circuits (hereinafter referred to as BCT) 113 and 123 for controlling the buses 140 and 141. L
The AP-B 111 manages a layer 2 protocol. The communication line 100 includes first and second CCEs 110 and 120 connected to a terminal or a host computer via a switch (communication line switching circuit, hereinafter referred to as SW) 101,
And the second system buses 140 and 141.

[0003] In addition, the LAP-B
111 and 121 are PRs of CCEs 120 and 110, respectively.
C122, 112 are connected to read / write lines 130, 131. Thereby, LAP-B111 and PR
C122 is connected to LAP-B via read / write line 130.
The contents of the status register 111 are read / written. Similarly, LAP-B 121 and PRC 112 are connected to read / write line 1
The contents of the status register of the LAP-B 121 are read / written via the interface 31.

[0004] Here, the SW 101 indicates a case where it is connected to the CCE 110 side.
CE 120 is used as a standby system. In this operation state,
In the standby system switching, the suspension information in the execution register holding the LAP-B protocol status of the active system is transferred to the standby LA system.
By transferring to the execution register of the P-B circuit, at the end of the active / standby system switching, L
The operation can be continued and resumed with the AP-B circuit 121 as a new active system.

The above-described conventional duplex communication system or circuit has the following problems.

First, in the prior art, when there is no response (response) from the communication partner to the transmission to the communication line, the cause is whether the transmission function of the LAP-B section of the working CCE is abnormal or not. It cannot be determined whether the terminal or the host computer that is the communication partner is abnormal. Therefore, the host device that switches the SW 101 cannot immediately switch the CCE. CCE switching must be performed after a timeout for a predetermined number of retransmissions. After switching, the CCE switching must be started by link open means, and communication is temporarily interrupted. The reason is,
LAP with only one operating CCE because the communication line is connected only to the working CCE by SW
This is because this state cannot be avoided in -B communication.

Secondly, in the prior art, since the communication line is connected only to the working CCE by the SW, if there is an abnormality in the receiving function of the LAP-B section of the working CCE, the communication is performed. Inability or temporary interruption of communication. The reason is that, since the communication line is connected only to the working CCE by the SW, when transmission starts from reception, when the receiving function of the working CCE is abnormal, it cannot be detected by the host device. Therefore, CCE switching cannot be performed, and communication is disabled or communication is temporarily interrupted.

[0008] In other words, the LAP-B protocol (X,
25) is a protocol premised on 1: 1 operation, so that even if the circuit or device of the prior art is duplicated, no instantaneous interruption or quasi-instantaneous interruption cannot be performed, and once a line interruption occurs. There was a problem that only recovery from the state could be performed.

An object of the present invention is to provide a redundant communication circuit having a first LAP-B and a second LAP-B for one LAP-B communication line when a failure occurs in an active LAP-B, and promptly returns to a standby LAP-B. -B, and to provide a duplex communication circuit for switching without interrupting LAP-B protocol communication.

[0010]

In order to solve the above-mentioned problems, the duplex communication circuit according to the present invention employs the following characteristic configuration.

(1) In a duplex communication circuit, which is connected between a communication line and a bus to a reception and transmission buffer and has first and second protocol communication control devices for performing LAP-B protocol communication control, The line has a communication line for reception and a communication line for transmission, and the first and second protocol communication control devices simultaneously receive signals from the communication line for reception and transmit the transmission signal via a transmission switching unit. A duplex communication circuit provided with a communication management controller that outputs to a trusted communication circuit and sends a transmission switching signal to the transmission switching unit.

(2) The duplex communication according to (1), wherein the first and second protocol communication control devices include a LAP-B receiving unit and a LAP-B transmitting unit respectively connected to the receiving and transmitting communication lines. circuit.

(3) The first and second protocol communication control devices are connected between the LAP-B receiving unit and the LAP-B transmitting unit, and include a protocol controller for comparing a transmission state and a reception state. 2) Duplex communication circuit.

(4) First and second protocol communication control devices each having substantially the same configuration, a communication management controller for managing / controlling the communication state of both protocol communication control devices, and transmission from the communication management controller A duplex communication circuit comprising: a transmission switching unit that selects a transmission signal of the first or second protocol communication control device according to a switching signal and outputs the selected signal to a transmission communication line.

(5) The duplication of (4), wherein the communication management controller is connected to each of the communication management controllers by a state monitoring bus, and receives a control signal from a protocol controller provided in the first and second protocol communication control devices. Communication circuit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a duplex communication circuit according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a preferred embodiment of a duplex communication circuit according to the present invention. The duplex communication circuit includes first and second CCEs 70 and 80 connected in parallel between the reception and transmission communication lines 10 and 20 and the reception and transmission buffer buses 50 and 60, the transmission switching unit 30, and the communication management controller. 40.

The first CCE 70 is a LAP-B receiving unit 7
1, LAP-B transmission unit 72, protocol controller 7
3 and buffer interfaces 74 and 75. Similarly, the second CCU 80 also includes a LAP-B receiving unit 81,
It comprises a LAP-B transmission unit 82, a protocol controller 83, and a pair of buffer interfaces 84 and 85.

The receiving communication line 10 includes first and second CCs.
It is connected to the LAP-B receiving units 71 and 81 of U70 and U80. The bus 50 for the reception buffer is connected to the LAP-B 70, 8
0 buffer interfaces 74 and 84.
The bus 60 for the transmission buffer is connected to buffer interfaces 75 and 85. The communication management controller 40 and the protocol controllers 73 and 83 are interconnected by a state monitoring control bus. Further, the communication management controller 40 sends a transmission switching signal to the transmission switching unit 30, and transmits the transmission signals from the LAP-B transmission units 72 and 82 via the transmission switching unit 30 to the transmission communication line 20.
To be sent to the user.

As will be described later, the protocol controllers 73 and 83 of the CCEs 70 and 80 transmit the transmission sequence number and the reception sequence number in the control unit signal, which is the communication protocol of the LAP-B, and the transmission state variable and the reception state variable in the CCE. Manage and control. Thus, the validity of the received and transmitted data is determined, and a procedure such as retransmission is executed.

FIG. 3 shows a frame format of a signal transmitted and received by the duplex communication circuit. As shown in FIG. 3, the frame format includes a flag section, an address section,
It comprises a control signal section, an information data section, a frame check and a flag section.

Next, the operation of the duplex communication circuit of FIG. 1 will be described. The LAP-B communication is roughly classified into a command starting from transmission and ending with reception, and a response starting from reception and transmitting. Each of these operations will be described below.

First, at the time of a command, a transmission request is transmitted to the communication management controller 40 from a higher-level device (not shown). Therefore, this communication management controller 40
In addition to E70 and E80, a transmission state variable and a reception state variable for management are internally provided.

Referring to the transmission state variable and the reception state variable of the first and second CCEs 70 and 80, if the state variables in the CCEs 70 and 80 are different from those in the communication management controller 40, they are set in the CCEs 70 and 80. . If they are correct (match), the CCEs 70 and 80 are notified that there is a transmission request, and both CCEs 70 and 80 are operated to perform data transmission. At this time, the communication management controller 40 sends a switching signal to select one of them to the transmission switching unit 30 so that both CCEs 70 and 80 perform data transmission at the same time, but actually output to the transmission communication line 20. The communication information to be transmitted is only the transmission data of the selected CCE 70 or 80.

In response to this transmission data, response reception data is received by two CCEs 70 and 80, and
The protocol controllers 73 and 83 of 0 compare the transmission state variable and the reception state variable in the CCE, and the transmission sequence number and the reception sequence number in the control unit data. After judging the validity by this comparison, the communication management controller 40 is notified that the transmission has been completed. Therefore, the communication management controller 40 checks the transmission state variable and the reception state variable of each CCE based on the transmission end notification from both CCEs 70 and 80, and updates the transmission state variable and the reception state variable for management.
If the received data is merely a response, the host device is notified of the end of transmission and ends.

For example, if the received data is a retransmission request or a response times out, the communication management controller 40 gives a retransmission instruction to both CCEs 70 and 80 according to the LAP-B protocol. The transmission switching signal to the transmission switching unit 30 switches the first transmission and the second transmission CCE by outputting a selection signal of the CCE 80 or 70 opposite to that at the time of the previous transmission. That is,
When the number of retransmissions of the LAP-B protocol (hereinafter, referred to as N2) is 2 or more, by switching the CCE, when the transmission function of the CCE is abnormal, it is possible to return without waiting for N2.

Next, the operation of the duplex communication circuit at the time of response will be described.

At the time of response, both CCEs 70 and 80 simultaneously receive the same reception data, and the respective protocol controllers 73 and 83 transmit and receive the transmission state variables and reception state variables in the CCE, and the transmission sequence number and reception sequence number in the control unit data. Compare. After judging the validity, the communication management controller 40 is notified of the reception.

The communication management controller 40 controls each CCE 7
Each of the CCEs 70,8
The transmission state variable and the reception state variable of 0 are checked to determine the validity of the reception operation. Then, the transmission state variable and the reception state variable for management are updated, and one of the CCEs 70 or 80 is updated.
Only give the receive buffer access permission to. Only the CCE 70 or 80 that has received the reception buffer access permission writes the reception data into the reception buffer. When the writing is completed, the communication management controller 40 is notified of the completion of the writing of the received data. The other CCE 80 or 70 discards the received data.

Upon receiving the reception data write completion from the CCE, the communication management controller 40 notifies the host device of the data reception. If there is no transmission instruction from the host device within a predetermined time, a simple response transmission instruction is issued to both CCEs 7.
0 and 80, and the transmission switching unit 30
A switching signal for selecting E is output and the processing ends.

As described above, since the CCEs 70 and 80 independently perform the transmission operation and the reception operation under the same conditions, they can operate without affecting the protocol operation in the protocol controllers 73 and 83. Further, the communication management controller 40
By selecting transmission from the CEs 70 and 80 to the outside, storage in the reception buffer, and transmission to the transmission communication line, it appears as if one CCE is operating, and stable communication can always be performed.

[0032]

Another embodiment of the present invention The transmission control section information from the communication management controller 40 is obtained simultaneously with the permission of transmission to the protocol controllers 73 and 83 included in the CCEs 70 and 80 of the preferred embodiment of the above-described duplex communication circuit of FIG. And a function to perform transmission. At this time, L of the first CCE 70
When there is a failure in the AP-B receiving unit 71, the communication management controller 40 compares the reception control unit information from the first CCE 70 with the reception control unit information from the second CCE 80, and finds that the LAP-B reception unit 71 of the first CCE 70 Failure can be detected. At this time, since the transmission control unit information generated by the protocol controller 73 of the first CCE 70 is incorrect, the communication management controller 40 provides the transmission control unit information notified from the second CCE 80 to the protocol controller 73 of the first CCE 70. Transmission information can be generated correctly.

That is, reception = first CCE 70 and transmission = first CCE 70, reception = first CCE 70 and transmission = second CCE
CE80, reception = second CCE80 and transmission = first CCE
70, reception = second CCE 80 and transmission = second CCE 80
The following four operations are possible. The communication management controller 40 can be realized using a high-speed CPU.

The configuration and operation of the embodiment of the duplex communication circuit according to the present invention have been described above in detail. However, it should be understood that the present invention should not be limited to only such specific examples, and that various modifications can be made without departing from the spirit of the present invention.

[0035]

As will be understood from the above description, the following remarkable effects can be obtained by the dual communication circuit of the present invention.

First, as soon as a CCE function failure is detected, the CCE is switched to the spare (other) CCE, so that there is no interruption in communication. The reason is that, in the LAP-B protocol, even if there is an error in the CCE, the retransmission procedure is performed up to N2 times. Since the stepping, the communication is interrupted for several seconds. According to the present invention, a pair of CCEs are operating at the same time, which is monitored in real time (real time) by the communication management controller 40, and an appropriate (normal) CCE is selected. This is because communication can be restored without waiting for N2 retransmissions.

Second, according to the duplex communication circuit of the present invention, stable communication can always be performed. The reason is that the communication management controller 40 selects the signal to the outside of the CCE, that is, the storage in the reception buffer and the transmission to the transmission communication line, and makes it appear as if one CCE is operating. This is because the CCE performs the processing of the received signal and the transmission processing completely in parallel, and the operation of the CCE can be performed without difficulty and stable communication can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a preferred embodiment of a duplex communication line according to the present invention.

FIG. 2 is a block diagram of a conventional duplex communication circuit.

FIG. 3 is a frame format of a transmission / reception signal of a duplex communication circuit.

[Explanation of symbols]

Reference Signs List 10 communication line for reception 20 communication line for transmission 30 transmission switching unit 40 communication management controller 50 bus to reception buffer 60 bus to transmission buffer 70, 80 CCE (LAP-B protocol communication control device) 71, 81 LAP-B reception Unit 72, 82 LAP-B transmission unit 73, 83 Protocol controller

Claims (5)

[Claims] 1. A duplex communication circuit connected between a communication line and a bus to a reception and transmission buffer and having first and second protocol communication control devices for performing LAP-B protocol communication control. Has a communication line for reception and a communication line for transmission, wherein the first and second protocol communication control devices simultaneously receive signals from the communication line for reception and transmit the transmission signal via a transmission switching unit. A duplex communication circuit, comprising: a communication management controller that outputs to a communication circuit and sends a transmission switching signal to the transmission switching unit. 2. The apparatus according to claim 1, wherein said first and second protocol communication control devices include a LAP-B receiving unit and a LAP-B transmitting unit connected to said receiving and transmitting communication lines, respectively. 2. A duplex communication circuit according to item 1. 3. The first and second protocol communication control devices are connected between the LAP-B receiving unit and the LAP-B transmitting unit and include a protocol controller for comparing a transmission state and a reception state. The duplex communication circuit according to claim 2, wherein 4. A first and second protocol communication control device having substantially the same configuration, a communication management controller for managing / controlling a communication state of both protocol communication control devices, and transmission switching from the communication management controller. A transmission switching unit for selecting a transmission signal of the first or second protocol communication control device by a signal and outputting the selected signal to a transmission communication line. 5. The communication management controller according to claim 1, wherein each of the communication management controllers is connected by a state monitoring bus, and receives a control signal from a protocol controller provided in the first and second protocol communication control devices. 4. The duplex communication circuit according to 4.