JP2611478B2 - Response monitoring device for communication control unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention transmits framed data, and receives a response from a communication control unit for confirming that the data has correctly arrived at a receiving side by a response from the receiving side. Related to monitoring method.

[Prior Art] Conventionally, as an example of this type of communication system, there is an X.25 HDLC procedure defined by CCITT. The X.25 recommendation uses a single timer called the T1 timer, which starts or restarts the T1 timer when transmitting command frames and information frames with the P bit set to 1, and retransmits when the T1 timer times out before a response is returned. Error recovery operation such as the above.

In the HDLC procedure, in the information transfer phase, the transmitting side continuously transmits in the order of the transmission order number, the receiving side detects the continuity of the received transmission order number, and sends the transmission order number of the next received frame to the transmitting side. Respond by telling. The transmitting side activates or restarts the T1 timer at the time of transmitting the information frame, and can continuously transmit the untransmitted transmission frames until the maximum number of outstanding frames is reached. When the transmission sequence number received by the receiving side becomes discontinuous, this is reported to the transmitting side, and the transmitting side goes up to the transmission sequence number that the receiving side has received continuously and correctly, and repeats the transmission sequence number again Retransmit in order (reject procedure). As an option, if the receiving side receives only one missing transmission sequence number and receives it, it notifies the transmitting side of the missing transmission sequence number, and the transmitting side stops continuous transmission, retransmits the missing frame, and stops There is a secret reject procedure for resuming continuous transmission. Since the presence or absence of an error is determined by detecting continuity, the receiving side cannot transmit another retransmission request until one error state is recovered.

On the other hand, a scheme has been proposed in which the receiving side can issue another retransmission request during one error state in order to increase transmission efficiency. This is the receiving side sequence number N notified by the receiving side.
N (R) and N (S) = M that notify that (R) is continuously and correctly received up to N (S) = N (R) -1.
The (R) frame is notified separately to the M (R) requesting transmission, and another retransmission request can be made during one error state. In order to correct errors in the retransmission frame and errors in the retransmission request frame, in this method, the transmitting side starts a timer at the same time as the transmission of the retransmission frame, and if the response frame cannot be received within a predetermined time, retransmits the frame again. Send. The receiving side starts a timer at the time of transmitting the retransmission request frame, and if the desired frame cannot be received within a predetermined time, transmits the retransmission request frame again.

[Problems to be solved by the invention]

In the conventional HDLC procedure described above, the number of timers is one, but since the presence or absence of an error is determined by detecting continuity, the receiving side transmits another retransmission request until it recovers from one error state. There is a drawback that efficiency cannot be improved when errors are relatively large. In order to improve the efficiency, N (R) for notifying that the receiving side sequence number N (R) is continuously and correctly received up to N (S) = N (R) -1;
(S) = M for requesting transmission of a frame of M (R)
(R), the transmission side is notified to the transmission side, and the error of the retransmission frame or the error of the retransmission request frame is monitored by the timer. In the method, both the transmission side and the reception side can transmit the retransmission frame and the retransmission request frame within the round-trip delay propagation time. Independent timers for the maximum number are required, and the control becomes complicated.

[Means for solving the problem]

According to the present invention, a response of a communication control unit that transmits a frame of a fixed length with a transmission sequence number and determines whether or not the frame has been received without error by the receiving side based on a response from the receiving side. In the monitoring device, a timer that generates an interrupt at a fixed time interval equal to the transmission time of the frame, and determines whether or not a response is received after the transmission of the frame is completed, and if not returned, retransmits the frame. Transmission control means for controlling, a memory for storing a transmission sequence number of a fixed number of frames continuously transmitted from the time when the frame is transmitted to the time when the response is returned, and the memory for storing the transmission sequence number for each interruption from the timer. The transmission sequence number of the frame is stored in the memory, and the transmission sequence number which has been stored most recently among the fixed number of transmission sequence numbers stored so far is taken out and transmitted. Timer monitoring means for notifying the control means, wherein the transmission control means notifies the timer monitoring means of the transmission sequence number of the transmitted frame for storage in the memory, and the transmission order notified from the timer monitoring means. When it is determined that a response to the numbered frame has not been returned from the receiving side, a response monitoring device of the communication control unit is characterized in that the frame is retransmitted.

〔Example〕

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

FIG. 1 is a block diagram of a communication control unit using a response monitoring method according to one embodiment of the present invention.

In the figure, 14 is an upper layer interface, 15 is a timer circuit, 16 is an 8-bit general-purpose CPU, 17 is a ROM (Read Only Memory) on which an entire control program including a flowchart shown in FIG. 18 is DMAC (Direc
t Memory Access transfer controller), 19 is RAM (Ramdom Acces
s Memory). Reference numeral 20 denotes a communication LSI.

FIG. 2 shows an inter-task interface of transmission control executed by the CPU 16. In the figure, 21 indicates a timer monitoring task, 22 indicates a transmission task, and 23 indicates a transmission driver. The operation of the timer monitoring task 21 will be described later with reference to FIG. When there is a retransmission request (= communication sequence number) N ₂ (S) from the timer monitoring task 21, the transmission task 22 determines whether or not a response already received from the receiving side has been returned from the N ₂ (S). If it has not returned, it queues in the transmission driver 23 to retransmit N ₂ (S). If there is no retransmission request, or if a received response has been returned even if there is a retransmission request, it is checked whether there is a transmission request (= communication sequence number) N ₁ (S) from the upper layer interface 14. If there is a transmission request N ₁ (S), it queues in the transmission driver 23 to transmit N ₁ (S). Transmission driver 23
If N ₁ (S) or N ₂ has (S) in the queue, the DM in FIG.
The AC 18 is activated to transfer the N ₁ (S) or N ₂ (S) data (transmission order number) in the RAM 19 to the communication LSI 20. The communication LSI 20 receives this and converts the data into a frame and transmits it to the line.

FIG. 3 is a flowchart of a timer monitoring task executed by the CPU 16 of the communication control unit shown in FIG. In the figure, 1 is the start of the process of the timer monitoring task 21 of FIG.
The transmission task 22 queues the transmission sequence number N ₃ (S) in the timer monitoring task 21 at the time of transmitting a frame by determining whether there is a frame transmitted by the transmission task 22 in FIG. 3 is a judgment whether the same value as the dequeued N ₄ (S) exists in the timer monitoring memory (part of the RAM 19) whose start address starts with START and ends with END, and 4 is the same as judgment 3 If the value is present it is a process of initializing 255 a portion thereof decimal (FF _H). Note that the timer monitoring memory is all initialized by FF _H at the start of communication, and the possible value of the transmission sequence number is modulo 128, that is, 0 to 127. 5 is a process for temporarily saving the contents of the timer monitoring memory indicated by the address pointer P to the register OUT, 6 is a process for inputting the dequeued N ₄ (S) in the process 3 to the memory indicated by the address pointer P, and 7 is The increment of the address pointer P, 8 judges whether or not the address pointer P has exceeded the end address END, and 9 shows the initialization processing of the address pointer P, and shows the updating of the address pointer P in processes 7, 8, and 9. 10 is a judgment as to whether or not the output from the temporarily saved timer monitoring memory is FF _H , 11 is a retransmission request to the transmission task 22, and 12 is the contents of the timer monitoring memory indicated by the address pointer P. register
Processing of temporarily saving the OUT, 13 is the processing to initialize the timer monitoring memory indicated by the address pointer P by the value FF _H, 14 is the outlet of the timer monitoring tasks.

In this embodiment, the communication control unit transmits a frame of a fixed length. The timer monitoring task is started by interruption at a fixed time interval equal to the frame transmission time. When the timer monitoring task is executed in the processing 1, the presence or absence of the dequeued N ₄ (S) of the transmitted N ₃ (S) from the transmission task 22 is checked in the judgment 2, and if there is no processing, the processing 13 is performed. Perform decision 3. Determining 3 performs search the same transmission sequence number and a timer monitoring N ₄ (S), the initializing it to a value FF _H treated 4 if there. Initialized to all values FF _H the same transmission sequence number in the timer monitoring memory at decision 3 and processing 4. When this is completed, in process 5, the address pointer P
The contents of the timer monitoring memory indicated by
In step 6, N ₄ (S) is input to the address. Determination after updating address pointer P in processes 7, 8, and 9
In checking the output of the watchdog timer memory saved in the register OUT, N ₂ (S) value FF _H unless its value is determined to have timed out, a retransmission request at 11. Determining a timer contents of the monitoring memory indicated 2 in Sent N ₁ (S) if the no treatment 12 with the address pointer P is temporarily saved in register OUT, and initializes the same memory in the process 13 with the value FF _H, treatment Execute 7. The subsequent processing is the same as described above.

〔The invention's effect〕

As described above, according to the present invention, a communication control unit that transmits a frame with a transmission sequence number and determines whether or not this frame has been received without error by a receiving side based on a response from the receiving side. Input the transmission sequence number of the frame transmitted continuously until the response is returned and store the memory that can be stored and the transmission sequence number when transmitting the frame. And a control means for judging that if no response to the frame of this transmission sequence number has been returned by this time, this response will not be received thereafter. Timer monitoring of responses to individual frames sent without multiple timers in an efficient communication scheme that can perform recovery There is a possibility to become effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart of an inter-task interface executed by the CPU of the communication control unit of FIG. 1, and FIG. 3 is a communication control unit of one embodiment of the present invention. 9 is a flowchart of a timer monitoring process of FIG. 1 ... Entry of the timer monitoring task, 2 ... Judgment of the presence or absence of the frame transmitted by the transmission task, 3 ... Judgment of whether or not the same value as the dequeued N (S) exists in the timer monitoring memory, 4 …… Memory initialization processing, 5… Temporary saving of memory contents, 6… Memory input processing, 7… Increment of address pointer P, 8 …… Judge whether P exceeds end address END , 9... P initialization processing, 10... Judgment whether the output from the memory is FF _H , 11.
... retransmission request to the transmission processing task, 12 ... temporarily save of memory contents, 13 ... memory initialization processing, 14 ... exit of timer monitoring task.

Claims (1)

(57) [Claims] 1. A response monitor of a communication control unit for transmitting a frame of a fixed length to which a transmission sequence number is attached, and judging whether or not the frame has been received without error by the receiving side based on a response from the receiving side. In the device, a timer that generates an interrupt at a fixed time interval equal to the transmission time of the frame, and determines whether or not a response is received after the transmission of the frame is completed. Transmission control means for controlling the transmission order number of a fixed number of frames transmitted continuously during the time from the transmission of the frame until the response is returned, for each interruption from the timer, The transmission sequence number of the transmitted frame is stored in the memory, and the transmission sequence number that has been stored most recently among the fixed number of transmission sequence numbers stored so far is read. And a timer monitoring means for notifying the transmission control means, wherein the transmission control means notifies the timer monitoring means for storing a transmission sequence number of the transmitted frame in the memory, and the timer A response monitoring device for a communication control unit, which retransmits the frame when it is determined that a response to the frame of the transmission sequence number notified from the monitoring unit has not been returned from the receiving side.