JPS6363241A - Data serial transmission system - Google Patents

Abstract

PURPOSE:To recognize the termination of the serial transmission of binary data and to attain data transmission by giving a data end recognition signal as well as the stop bit of a final code in transmission data. CONSTITUTION:With a change from a high level to a low level after the recognition of the stop bit SP, a reception circuit 21 starts a session of detecting a start bit ST. When the circuit 21 reaches the detection session, it generates a pulse showing the detection of the start bit. When the level of a transmission line 30 is recognized at a low level, the low level state is detected to be the start bit ST. A transmission data reception end detection circuit 23 receives a message when the level of the transmission line 30 returns to a high level from a low level, while the reception circuit 21 is measuring the start bit detection session. A data end detection signal is formed until the start bit detection pulse is generated, and the detection of transmission data termination is outputted. Even if the data end detection signal is formed with a pseudo pulse on the transmission line in the middle of data transmission, it can be handled as the interruption of data transmission.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an asynchronous data serial transmission system.

[Conventional technology]

In the conventional asynchronous data serial transmission system, a start bit is placed at the beginning of the binary signal string for each code to be transmitted on the transmitting side.
In addition, a special bit signal called a stop bit is added to the end of the transmitter, and it is transmitted intermittently in code units at a predetermined speed based on the transmitter's internal clock.When the receiver detects the start bit, it starts its own clock. This method determines the length of one word from the time when the signal sequence following the start bit is received until the stop bit is received.

[Problem that the invention seeks to solve]

The conventional asynchronous data serial transmission method described above is -
For example, ASCII in which 7 bits are formed into one code unit
Or, in the case of JIS codes, a final code is set in the control code to identify the end of transmission of one data.
In pure binary data transmission, the length of one word is identified only by the start bit and stop bit, so the receiving device cannot recognize the final code of the data, and assumes that an interruption in data transmission is a failure and retransmits it. There is a problem in that it is practically impossible to transmit binary data in a system that is in a request state.

SUMMARY OF THE INVENTION An object of the present invention is to provide a data serial transmission system that solves the above problems.

[Means for solving problems]

In the data serial transmission method of the present invention, in an asynchronous method,
The transmitted data has an end-of-data recognition signal following the stop bit of the final symbol.

〔Example〕

Next, the data serial transmission system of the present invention will be explained with reference to the drawings.

FIG. 1 is a time chart of signals on a transmission line showing an embodiment of the present invention. In FIG. 1, after serially transmitted data is transmitted from the first symbol to the final symbol, a data end recognition signal (DE) is transmitted. Serial transmission data is provided with a start bit (ST) and a stop bit (SP) before and after each binary code forming the data using a well-known technique. Normally, the signal is at a high level when the transmission path is capable of transmitting data, and the start bit (ST) changes from high level to low level. Further, the stop bit (sp) continues to be at a high level.

FIG. 2 is a block diagram showing an example of the transmission line connection portion of the transmitter and receiver of the present invention. In Figure 2,
The transmitting device 10 includes a serial data forming circuit 11. Transmission circuit 12
．． and an end recognition signal forming circuit 17313. The receiving device 20 includes a receiving circuit 21, a data reading circuit 22. and a reception end detection circuit 23. Serial data formation circuit 1
1 forms data into the above-mentioned code structure that is compatible with the asynchronous transmission method. The transmitting circuit 12 is driven by the serial data forming circuit 11 to drive the transmission path 30, and sequentially extracts and transmits serial codes. The end recognition signal forming circuit 13 receives the notification of the end of transmission data from the serial data forming circuit 11, forms a data end recognition signal, and sends it to the transmission line 30 via the transmitting circuit 12.

On the other hand, the receiving circuit 21 receives the transmission code from the transmission path 30. The data reading circuit 22 converts the serial code and reads it into data. The reception end detection circuit 23 intercepts the received signal, detects a predetermined data end recognition signal, and notifies a control circuit (not shown) of the end of data.

Next, a method for recognizing the end of data will be described with reference to FIG. 3 together with FIGS. 1 and 2. FIG. 3 is a time chart showing an example of the data end recognition signal and this pressure testing method. From the transmission line 30, a stop bit (sp) is followed by a start bit (ST) or data end recognition signal D.
E is transmitted by changing the high level of the stop bit (SP) to low level. The length of the data end recognition signal (DE) is approximately 1/4 of the length of the start bit (ST>).
) After recognition, the start bit detection time period starts with the change from high level to low level. When the detection time period is reached, a start bit detection pulse is generated and the level of the transmission line 30 is set to low level. When confirmed, this low level state is detected as a start bit (ST).If the level of the transmission line 30 has returned to high level when the start bit detection pulse is generated, it is assumed that data transmission has not started. The transmission data reception end detection circuit 23 receives a notification when the level of the transmission line 30 returns from low level to high level while the reception circuit 21 is measuring the start bit detection time, and outputs a data end detection signal. It is formed until the start bit detection pulse is generated and outputs the detection of the end of transmission data.Even if the data end detection signal is formed by a pseudo pulse on the transmission path during data transmission, it can be treated as an interruption of the transmission data. Yes, no inconvenience will occur.

FIG. 4 is a time chart 1 showing an example of a start bit detection method in a receiving circuit according to a well-known technique. When one bit in the transmitting device is defined as the length of 16 clock pulses, the receiving device also has a clock having the same interval pulses as the transmitting device and a 16-pulse counting means. Further, the start bit detection time limit in FIG. 3 is set to the time when 8 clock pulses are counted.

In FIG. 4, clock pulses are continuously generated at predetermined intervals. When the input from the transmission path changes from high level to low level, the receiving circuit counts clock pulses and generates the first sample pulse for the opposite phase between the 8th and 9th pulses. This pulse is the start bit detection pulse shown in FIG. 3. Subsequently, clock pulses are counted and sample pulses are sequentially generated every 16 pulses at intervals from ping 1.

Along with this sample pulse generation, the level of the transmission line is checked, and so on. This continues until the tcode is read and a predetermined stop bit is detected. In this example, in order to make the data end recognition signal and the data end detection signal shown in FIG. 3 almost the same length, the data end recognition signal is made to have a length of four clock pulses.

In the above embodiment, the start bit detection pulse is set at approximately the center of the start bit, and the length of the data end recognition signal and the detection signal are set to be approximately the same. However, the position and length of the pulses are not limited by the above description. Further, the block configuration shown and described in FIG. 2 is an example, and the present invention is not limited to the above description.

〔Effect of the invention〕

As explained above, the data serial transmission system of the present invention has a data end recognition signal following the stop bit of the last code of transmission data in an asynchronous system, so that even binary data can be recognized by recognizing the end of serial transmission data. This has the effect of allowing data transmission.

[Brief explanation of drawings]

FIG. 1 is a time chart showing an embodiment of the data serial transmission system of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a partial operating unit I in the receiving device of FIG. FIG. 4 is a time chart illustrating sample pulse generation in an asynchronous receiver. 10... Transmitting device, 13... Termination recognition signal forming circuit, 20...- Receiving device, 23...
...Reception end detection circuit, 30...Transmission line, D
E... Data end recognition signal, ST...
Start bit, SP... Stop No. IWJ-1 whisper! 77 things to do ←Figure 2

Claims (1)

[Claims] An asynchronous data serial transmission system characterized in that transmission data has a data end recognition signal following a stop bit of the final code.