KR930004100B1 - Method for embodying full duplex communication protocol - Google Patents

Abstract

The method for realizing the protocol improving the data communication speed and quantity per unit time comprises steps: (a) transmitting the first frame composed of an initial frame number, a control code (ENQ), and a frame end code (ETX) at the transmission part; (b) requesting the receiving time for next frame at the reception part when receiving the first frame; (c) transmitting the second frame in sequence of frame number, which and composed of a frame number, a data start code (STX), data and frame end codes (ETX,EOT), and retransmitting the corresponding frame in sequence when receiving the NAK frame; and (d) transmitting the second frame having a last frame number, a control code (ACK), and the EOT when receiving the second frame having the EOT, or transmitting the second frame having an errored frame number, NAK, and the EOT when checking the errored frame.

Description

Asynchronous full duplex protocol implementation

1 is a block diagram of an asynchronous communication system configuration.

2 is a memory map configuration diagram for carrying out the present invention.

3 is a frame diagram for carrying out the present invention.

4 is a flow chart of the present invention.

5 is a protocol flow diagram in accordance with the present invention.

* Explanation of symbols for main parts of the drawings

11,21: CPU 12,22: ROM

13,23: RAM 14,24: Timer

15,25: I / O

The present invention relates to a data communication method of a communication system, and more particularly, to a method capable of implementing a bidirectional data communication protocol in a full-duplex communication system in an asynchronous communication system.

1 is composed of a first communication system and a second communication system using a communication network as a medium, and each communication system stores CPUs 11 and 21 and system operation and control programs that control hardware and software of the entire system. ROM 12 and 22, RAM 13 and 23 for temporarily storing data generated during program execution, and Timer 14 for generating a timer signal relating to time and informing the CPU 11 and 21. 24, the I / O (15, 25) that controls the CPU (11, 21) to control the input and output of data, and a communication line that transfers the data of the I / O (15, 25) to the communication network. The furnace 30 is comprised.

The communication system of FIG. 1 uses an asynchronous scheme. In general, the protocol of the asynchronous scheme uses a half duplex scheme. That is, one formatted message is sent to the other party and waits without transmitting the next message until a response is received. Therefore, in the asynchronous half-duplex communication, the next message is transmitted only when a response indicating that the message format is normal between the transmitting and receiving systems is received. For example, in FIG. 1, if the transmitting side is the first CPU 11 and the receiving side is the second CPU 21, the first CPU 11 transmits one message promised to both parties to the second CPU 21. In this case, the second CPU 21 analyzes the received message and transmits a response message of the first CPU 11 in response thereto. Then, the first CPU 11 analyzes the response message, recognizes that the second CPU 21 has normally received the message, and transmits the next message to the second CPU 21 again.

However, when the half-duplex communication method is used in the asynchronous communication system as described above, there is a problem that the data communication speed becomes very slow and the amount of data that can be communicated per predetermined time is also very small.

Accordingly, an object of the present invention is to provide a method capable of implementing a bi-directional data communication protocol in a full duplex in an asynchronous communication system.

Another object of the present invention is to provide a method for improving the data communication speed and the amount of communication per unit time by implementing a full-duplex protocol in a simple manner in an asynchronous communication system.

Hereinafter, the present invention will be described in detail with reference to the drawings. The configuration diagram of a communication system for carrying out the present invention is the same as that of the first diagram, and the reference numeral is the same as the first diagram.

2 is a diagram illustrating a memory map for implementing the present invention. Here, (2A) and (2F) is a configuration diagram of the transmission message buffer and the reception message buffer, and the transmission message buffer 2A is a buffer in which data to be transmitted through the I / O (15, 25) from the upper layer is stored. The message buffer 2F is a buffer for storing a received message and transmitting it to a higher layer.

2B is a configuration diagram of a frame buffer, which is a buffer for storing up to seven frames in one frame unit for protocol implementation before being sent from the transmission message buffer 2A to the transmission buffer 2C.

(2C)-(2E) is a configuration diagram of the transmission buffer, the reception buffer, and the temporary buffer, and the dual transmission buffer 2C is for transmitting on the communication line 30 by the interrupt of the I / O (15, 25). Receiving buffer 2D is a buffer for storing data. The receiving buffer 2D is a buffer in which I / O 15, 25 reads and stores the data received on the communication line 30 by interrupt, and the temporary buffer 2E is I. It is a two buffer that temporarily stores one frame so that each process can analyze the contents of the receiving buffer 2D read by the interrupt of / O (15, 25). A buffer such as (2A)-(2F) is allocated to the RAMs 13 and 23, and the dual transmit message buffer 2A and the receive message buffer 2F have a maximum size of 1 message of 256 bytes. Terminating with an ETX code, the receipt of the message n depends on the size of the buffer. The frame buffer 2B has a maximum size of one message of 256 bytes, ends with an ETX code, and the maximum number of messages is seven. The transmit buffer 2C, the receive buffer 2D, and the temporary buffer 2E are n, 256, the number of bytes, and the points are traversed (eircular queue).

3 is a frame data structure diagram of the present invention. Here, (3A) is a sync frame (SYN frame), which is in the form of a frame for synchronizing or responding with the other communication system before transmitting the first frame stored in the frame buffer 2B. Among the components of the sync frame, fn is a frame number, ct1 is a control code, and 'ENQ' for synchronization with the other party and 'ACK' and 'NAK' for response to the other party. End is a frame end code, and 'ETX' and 'EOT' are loaded, and bcc is check-sum data. And (3B) is a SOH (Start Of Head) frame, which is stored in the frame buffer 2B and communicated by carrying messages between the two parties via I / O (15, 25). STX is the data start code.

4 is a flowchart of the present invention. 4A is a flow chart of the receiving process, which analyzes the contents of the receiving buffer 2C that receives and stores data on the communication line by the interrupt of the I / O (15, 25), and then applies the protocol promised to both parties. It is the process of determining whether there is no abnormality.

And (4B) is a flow chart of the message process. If it is determined whether the contents of the transmission message buffer 2A are present, it is read and stored in the frame buffer 2B so as not to exceed a maximum of seven messages. Process.

4C converts each message stored in the frame buffer 2B into a frame form such as (3A) and (3B) promised by both parties, stores them in the transmission buffer 2C, and sends them to the other party. It's a process.

Also, (4D) is a process for processing a predetermined time required for the processes (4A) to (4C) as a time process.

FIG. 5 is a communication procedure in processing each frame, FIG. 5 (a) is a communication procedure proceeding normally, and FIG. 5 (b) is a communication procedure in receiving 'NAK' during transmission, and FIG. 5 (c) FIG. 5 is a flowchart illustrating a case in which a next frame is normally received after an undetermined frame is received. FIG. 5D is a diagram illustrating a communication procedure when a reception time is exceeded after 'NAK' transmission. The present invention will be described in detail with reference to FIGS. 1 to 5 according to the above-described configuration.

Based on the above-described configuration, the present invention will be described in detail with reference to FIGS.

It is assumed here that the first CPU 11 is the transmitting side, and the second CPU is the receiving side. Then, the first CPU 11 stores the message having the same frame structure as that of the third degree in the first RAM 13 in a form promised between the second CPU 21 and the data to the first I / O (15, 25). The first I / O 15, 25 generates an interrupt and transmits the formatted message of the first RAM 13 to the second I / O through the communication line 30. The second I / O 25 then generates an interrupt by the transmitted message to inform the second CPU 21 that the message has been received. At this time, the second CPU 21 reads the received message of the second I / O 25, stores the received message in the second RAM 23, and analyzes it to determine whether it is normal. At this time, if the received message is not normal, the second CPU 21 transmits a response message 'NAK' to the first CPU 11 in the same procedure as the above procedure, and if normal, the message received from the first CPU 11 is the last. The response message 'ACK' is transmitted only when the 'EOT' message indicating the frame is received.

In addition, when the first CPU 11 and the second CPU 21 determine that a predetermined time is necessary for the communication procedure of the above message, the corresponding time is registered and then time service is received through the timers 14 and 24. Process.

In order to implement full-duplex in the asynchronous communication system as described above, there are four processes. The basic level is the same as (4C). All frames stored in the frame buffer 2B in the transmission process (up to 8 ) And the other side analyzes each frame in the receiving process such as (4A), and if the frames (frames ending with EOT) are all received normally, the 'ACK' is sent to the frame Ctl area such as (3A). 'Completes the communication by sending the recorded response message. The determination of the 'EOT' frame is not transmitting the last one frame of the frame buffer 2A in the transmission process such as (4A), and the message time required by the message process such as (4B) has been exceeded or the frame buffer has been exceeded. This is when all seven frames are stored in (2B). In addition, retransmission is retransmitted from the 'NAK' frame number such as (3A) or frame 0 such as (3A) when the 'NAK' frame is received from the other party's receiving side or the transmission time required by the transmission process such as (4C) is exceeded.

Where (4A) is a transmission process performed each time one byte of data is received from I / O (15, 25), and (4B) is a message process performed whenever one message is sent to the lower layer in the upper layer. (4C) is a transmission process performed each time a frame is transmitted from each process, and (4D) is an O / O provided to the timers 14 and 24 when the time required by each process is exceeded. It is generated by S (Operating System).

The process at the time of transmission is demonstrated.

First, when you want to send a message, you have to move the message from the upper layer to the lower layer. In this case, the message process starts as shown in (4B). In other words, if the message process is driven, it is checked whether it is in the standby mode in step 141. In the transmission mode, in step 142, the message stored in the transmission message buffer 2A is stored in the frame buffer 2B. However, if it is determined in the standby mode in step 141 that the EOT frame is transmitted in the transmission process as shown in (4C), the message is not read from the transmission message buffer 2A because the 'ACK' frame is waiting to be received. .

When the message to be transmitted is completely stored in the frame buffer 2B through the above message process, the transmission process as shown in (4C) is driven. At this time, since the frame buffer 2B stores a maximum of seven frames, such as synchronous frames excluded from (3B) such as (3A), there are eight frames to be transmitted in the transmission process. Therefore, if the transmission process is driven (step 151), it is checked whether the frame number to be transmitted is "0", and if the transmission frame number is found to be "0", a synchronization frame such as (3A) is created in step (152). Stored in the transmission buffer 2C. In this case, the sync frame is an 'ENQ' frame, and '0', ENQ 'and' ETX 'are inserted into the' fn ',' ctl 'and' end 'regions, respectively. In addition, when the frame number to be transmitted in step 151 is not '0', step (153) is performed to read the message of the corresponding frame number stored in the frame buffer 2B and convert the message into the frame form as shown in (3B). After that, the message of the frame form converted in step 154 is stored in the transmission buffer 2C. Therefore, when the transmission process is driven as described above, the contents of the frame buffer 2B are converted into the form of the frame promised to both parties so that they can be sent to the other party by sending interrupts of the I / O one frame in order of the frame number to be transmitted. The last one frame of the frame buffer 2B always causes a message process, such as 4 (B), to wait for the message to time out and wait until the standby mode is set, or until the eighth frame, and then transmit an 'EOT' frame.

Therefore, the sender performs a message process to store the message stored in the send message buffer 2A in the frame buffer 2B, and performs the send process to change the contents of the frame buffer 2B to (3A) and (3B). Convert to a frame format such as

Second, the process at the time of reception is explained. Data received through the communication line 30 is applied to the CPU (11, 21) through the I / O (15, 25), the CPU (11, 21) receives the RAM (13, 23) by one byte Store in the buffer 2D. At this time, the reception process as shown in (4A) is driven. First, in step (101), one byte of data is read from the reception buffer 2D, analyzed, and sequentially written to the temporary buffer 2E. At this time, if it is determined that an error such as an over rum or parity is performed in step 102, an error flag is set and terminated in step 103, and ETX or EOT in steps 104 and 105. If it is determined that the message has been received in one frame or all messages in eight frames have been received, the procedure proceeds to a routine for analyzing the byte data stored in the temporary buffer 2E. In other words, if it is found to be ETX or EOT, in step 107, the data of the corresponding byte is stored in the temporary buffer 2E, and in step 108, 'bcc' of the frame is read from the reception buffer 2D. Thereafter, in step (109) and (110), an error flag is set or 'bcc' is checked. If an error flag is set or 'bcc' is in an abnormal state, as in (3B) in step (118), Check if the frame starts with SOH '. In this case, if the frame starts with 'SOH', it is checked whether the 'NAK' frame is already transmitted. If the 'NAK' frame is not transmitted, the message process (4B) and (4C) in step 120 are performed. The transmission process is driven to transmit a 'NAK' frame in the form of a frame such as (3A), and then the reception time is requested and ends.

However, if the error flag is not set in step (109) (110) or 'bcc' is found to be normal, it is checked whether the frame received in step (111) is a synchronization frame such as (3A). However, if the frame received in step 111 is a 'SOH' frame such as 3B, the process proceeds to step 121 to check whether the received frame number is normal. At this time, if the received frame number is not normal, it is checked whether the received frame number is larger than the received frame number. If the received frame number is larger, the frame to be received by proceeding to (119) and (120) above. Send 'NAK' frame with number and end. However, if the received frame number is small, the reception process ends. If the received frame number is normal in step 121, the contents of the current frame stored in the temporary buffer 2E are stored in the received message buffer 2F. If the reception time is requested in step 124, the reception time is canceled. In step 126, it is checked whether the content of the 'end' area of the current reception frame is 'ETX'. In this case, if there is a frame to be received in addition to the currently received frame, 'ETX' requests a reception time and ends in step 128. However, if the content of the 'end' area is not 'ETX' in step (126), it is 'EOT', and since there is no more frame to receive, it is possible to transmit an 'ACK'-frame such as (3A). In this case, a message process and a transmission process such as 4B and 4C are driven and performed, and an 'ACK' message is transmitted to the sender indicating that the 8-frame message has been normally received.

However, in step 111, the frame starts with 'SYN', and in step 112, it is checked whether the frame is an 'ACK' response frame. In this case, if it is 'ACK', since the transmitted frames are all normally transmitted to the receiver, when the transmission frame time is the same as the last frame number transmitted in the state of requesting transmission time in step (129) 130, the transmission time is canceled and terminated. Otherwise, ignore ACK and exit.

In addition, if it is determined as 'NAK' in step 113, an error occurs in a frame transmitted during frame transmission, and a request for retransmission of a frame message of the corresponding frame number is requested from the receiver. If it is found to be smaller than or equal to the number of, in step 133, the frame number to be transmitted is replaced with the frame number currently received (that is, the frame number in which an error occurs). If it is determined in step 134 that the transmission time has already been requested, then in step 135, the transmission time is released and ends.

In addition, if the reception frame is found to be an 'ENQ' frame in step 114, when the frame number to be received in step 115 is '0' times, in step 116, the reception time is requested and ends. However, if it is determined in step 114 that the state is not the 'ENQ' frame, the process ends after clearing the contents of the error flag reset and the temporary buffer 2E in step 117.

When the operation process of the reception process is integrated, after the contents of one frame are stored in the temporary buffer 2E, the contents of the temporary buffer 2E are analyzed and branched to the corresponding function processing program. At this time, the 'SOH' program is actually required data between the two. When the received frame numbers are received in order, they are stored in the reception message buffer 2F and sent to the upper layer. In addition, the 'ACK' program is a frame to be received when the last frame ('EOT' frame) is transmitted from the transmitting side, and therefore, should be received only when a transmission time is required. Therefore, when the transmission time is requested and the transmission time is requested, it recognizes that all transmitted frames have been normally transmitted to the other party and resets the standby mode.

Thirdly, the 'NAK' program means that the frame number transmitted from the other party to 'NAK' was abnormal during transmission, so it is changed from this frame number to the frame number to be transmitted in order to transmit again. The ENQ program is a frame indicating the start of communication between the two parties.

Finally, time processes like (4D) handle this when a certain amount of time is required for each process. That is, in the case of the transmission time, after transmitting the last 'EOT' frame in the transmission process, if it is determined that the transmission time is exceeded in step (161) while waiting for the 'ACK' frame, in step (162) the frame number to be transmitted ' After setting to '0', retransmit mode is set and retransmit from frame '0'. In the case of the reception time, when the last code of the frame is 'ETX', there is more next frame. If the reception time is exceeded, it means that the frame is lost during transmission. Therefore, if it is determined in step 163 that the reception time is exceeded, in step 164, the reception time is required after transmitting the 'NAK' frame. Finally, the message time is to check whether there are any more messages to send to the other party from the upper layer within a certain time. Therefore, the transmission process such as (4C) is driven to determine the 'EOT' frame. Therefore, if the message time is found to be exceeded in step 165, the standby mode is set in step 166.

The above flow is described with reference to FIG.

First, when data is normally communicated between the transmitting side and the receiving side as shown in (5A), the transmitting side system transmits frame 0 in the form of frame like (3A), and then continuously as frames 1-7. Send a 'SOH' frame like 3B. At this time, the receiving side requests a reception time in units of receiving frames and analyzes the corresponding frame state. When all eight received frames are normal, the receiver transmits an 'ACK' frame after receiving the last frame ('ENT').

Secondly, a case in which a transmitting side such as (5B) receives a 'NAK' frame during transmission will be described. In the case of (5B), an error occurs in the third frame among the frames transmitted from the transmitting side. Then, the receiving side determines that the frame error is completed when the third frame is received. At this time, the receiving side requests the reception time and transmits a 'NAK' to the transmitting side together with the frame number where the error occurred. Thereafter, the receiving side ignores the received frame until the frame of the 'NAK' frame number is received. At this time, when the 'NAK' frame is received, the transmitting side sequentially transmits frames from the corresponding frame number again.

Third, the operation process in the case where the next frame is normally received after receiving the undecided frame as shown in (5C) will be described. In the case of (4C), the third frame is determined to be an undeterminable frame, and the fourth frame is normally received. Even in this case, the receiver transmits 'NAK' as the third frame number and ignores the frame received thereafter. The transmitter transmits the remaining frames sequentially from the corresponding frame after receiving the 'NAK' frame.

Fourth, we look at the case where the reception time is exceeded after 'NAK' transmission as in (5D). At this time, in case of (4D), it is determined as an error of the third frame. In this case, the receiver requests a reception time and generates a 'NAK' frame of the corresponding frame number. At this time, the receiving side requests the receiving time again and generates a 'NAK' frame of the corresponding frame number if the contents of the 'NAK' frame are not received again so that the reception time is exceeded.

As described above, the full-duplex communication method can be used in the asynchronous communication system, thereby increasing the data communication speed and improving the data transfer rate per unit time, and making the protocol implementation simpler and easier than the synchronous full-duplex communication protocol. There is an advantage that can be done.

Claims (3)

A method of communicating data between a transmitting and receiving system in an asynchronous communication system, comprising: transmitting a first frame comprising an initial frame number, a control code ENQ for initial synchronization, and a frame end code ETX when a transmission message is generated at a transmitter; A first process, a second process of requesting a next frame reception time at a receiving side when receiving a first frame having an ENQ control code from the transmitting side, and a first frame transmission having an ENQ control code by performing the first process A third process of transmitting a second frame consisting of frame number, data start code STX, pure data and frame end code ETX, and EOT in order of frame number, and sequentially retransmitting from the corresponding frame when receiving a NAK frame; After performing the second process, the second frame sequentially received at the receiving end in frame units When receiving the second frame having the EOT frame end code, the second frame consisting of the last received frame number, control code ACK, and frame end code EOT is transmitted to the transmitting side, and when frame error occurs, an error occurs frame number, control code NAK, frame And a fourth process of transmitting a second frame made of an end code to a transmitting side. A method of transmitting data in an asynchronous communication system having a send and receive message buffer, a frame buffer, a send and receive buffer, and a temporary buffer memory map, wherein the send message buffer stores a transmission message generated to a higher layer. Is stored in the frame buffer, the message processing process, and the first frame for synchronization with the receiving side when the first frame is transmitted at the time of one frame is stored in the transmission buffer, and the first frame is transmitted and stored in the frame buffer. Converts the message into a second frame including a frame number and stores the message in a transmission buffer, and stores the message stored in the reception buffer in a temporary buffer on a frame-by-frame basis. Analyze and store the response first frame according to the normal and frame error in the transmission buffer. In the transmission mode, the frames stored in the frame buffer in the message processing step are sequentially transmitted to the receiving side through the transmission processing step. In the receiving mode, the received messages are analyzed and transmitted in units of frames in the reception processing step. Method for implementing a full-duplex communication protocol of the asynchronous type, characterized in that it operates to transmit to the side. The method of claim 2, wherein the reception process is performed by synchronizing with the transmitting side when receiving the first frame (ENQ) from the transmitting side, and the second frame to be received when receiving the second frame (SOH) from the transmitting side after performing the above process. Analyzing the frame number and the current received second frame number and storing the contents of a normal temporary temporary buffer in a reception message buffer so that a higher layer can be read; and checking whether the current received frame is the last frame after storing the received second frame. Storing a first frame (ACK) in the transmission buffer in order to respond to the sender a normal reception completion state only at the last frame date, and when the current received second frame number is larger in the process of analyzing the second frame number, a frame error Asynchronously characterized in that the second frame (NAK) is stored in the transmission buffer to respond to the state Full-duplex communication method implemented in the formula.