JPH0630493B2 - Asynchronous data communication synchronization method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for establishing synchronization between two stations when performing asynchronous data communication between two stations (for example, between a master station and a slave station) using weak radio waves, and particularly communication The present invention relates to a method of adding a notice signal for synchronization to communication data so that synchronization can be easily performed even when noise is mixed in radio waves. In the following drawings, the same reference numerals indicate the same or corresponding parts. Further, logic or levels “High” and “Low” are simply described as “H” and “L”.

[Prior art]

Conventionally, there are a synchronous communication method and an asynchronous communication method as a method of synchronizing data communication between two stations (for example, a master station and a slave station) that communicate with each other. In the synchronous communication method, the master station always outputs a communication signal continuously, and periodically inserts a synchronization code in the signal to synchronize (synchronize) the signal between the master station and the slave station. It is something to do. In the present invention, a master station and a slave station communicate using radio waves,
At this time, the main purpose is mainly to use the slave station for a long time (several years) with a battery, but in such applications, the slave station receives continuous radio waves and synchronizes from it. The above-mentioned synchronous communication method for extracting the code has the merit of high-speed signal transmission, etc., because the slave station must always be operating, the battery life becomes short, and the control and logic contents inside the slave station become complicated. Although it is a certain method, it is not preferable. On the other hand, in the asynchronous communication system, the communication signal is output whenever the master station is needed, and the slave station only has to operate its communication means at this time, so the battery consumption is reduced and Suitable for use. That is, this asynchronous communication system is generally an NRZ signal and is composed of, for example, 11 to 12 bits of a start bit (1 bit), a data bit (8 bits), a parity bit (1 bit), and a stop bit (1 to 2 bits). A unit communication text in which a specified number of characters are connected at a specified interval (however,
The number of characters is sometimes given for each unit message using the first character of the unit message) and is transmitted and received at an arbitrary time interval within a fixed time (that is, asynchronously). In particular, no character for synchronization is added. Further, in this case, the long data to be transmitted is once divided into 8 bits, and a start bit, a parity bit, and a stop bit are added before and after each 8-bit segmented data thus divided and transmitted. . In this asynchronous communication method, synchronization from the end of data transmission to the output of the next data is normally performed by detecting a start bit after detecting a no-signal state (pause period) for a certain time or longer. During the communication idle period, the slave station is in a non-signal state, and the slave station detects this non-signal state and waits for a call from the master station. In a no-signal state, a slave station that has lost synchronization due to an abnormality in a received signal during communication is also in an interrogation waiting state, and synchronization is generally possible from the next reception. Here, when the slave station detects that no signal has passed for a certain period of time (timeout), it forcibly returns the operation of the slave station to the initial mode to synchronize the master station and the slave station. Further, the master station also establishes a pause detection time of a certain time when it determines that communication with the slave station is abnormal due to synchronization with the slave station, and performs synchronization with the slave station. FIG. 3 (1) shows the waveform of the reception demodulated signal of the slave station, and FIG. 3 (2) shows the timing of the operation mode (of the internal CPU) of the slave station. In FIG. 1 (1), 1 is a character, and a unit communication message is a character 1 in which a predetermined number of characters 1 are normally arranged at a predetermined interval. CPU of slave station
In (not shown), the start bit (not shown) of the first character of the unit communication text 10 is detected after the first pause period as shown in (2), and the reception processing mode is entered. Fig. 4 (1), (2)
Shows the signals sent and received by the parent and child stations, and Fig. 3 (3) shows the operating period of the child stations on a large time scale. Both (1) and (2) in the figure correspond to digital signals before or after demodulation. That is, in response to the interrogation signal 11 from the master station as shown in FIG. 1A, the slave station starts operation as shown in FIG. 3C,
In response to the request for the interrogation signal 11, a response signal 12 as shown in FIG. Fig. 5 is a time chart showing the synchronization operation. Fig. 5 (1) shows the airwaves (however, for convenience, it is the waveform of the digital signal before modulation or after demodulation), and Fig. 5 (2), (3) It shows the operating period of the station. Further, FIG. 2B shows the case where the slave station receives the interrogation signal 11 of the master station from the beginning, and FIG. 3C shows the case where the interrogation signal 11 is received from the middle. That is, as shown in Fig. 2 (2), the interrogation signal 11 (Fig. 5) from the master station.
The slave station which normally receives (1)) stops its operation when it completes the data transmission of the response signal 12 ((1) in the figure) in the correct sequence. However, the slave station that received the interrogation signal 11 of the master station from the middle cannot detect the start bit (not shown) of the first character in the interrogation signal 11 as shown in (3) of the same figure, and thus the same figure (1). Waiting while monitoring the transmitted radio waves until the airwaves such as are quiet. However, in this example, it is assumed that after the interrogation signal 11 of the master station ends, it waits until the response signals 12 of the other slave stations disappear. Further, after a certain pause determination time TW elapses after the aerial radio wave becomes quiet, the slave station first enters the interrogation waiting time TS1 for synchronization. However, when the noise 21 is received during the pause determination time TW, a new pause determination time TW after disappearance of the noise 21 is passed and then the interrogation waiting time TS2 is entered.

[Problems to be Solved by the Invention]

However, in asynchronous data communication using radio waves, various noises are received in a place where the ambient noise environment is poor. For example, in the case of FIG. 5, when new noise 21A is received, the next parent noise is received. The pause determination time TW required by the time when the interrogation signal 11 of the station is output cannot be detected, and the receiving station (in this case, the slave station) cannot always get out of the no-signal time detection mode.
There is a possibility that the read mode of the leading data for synchronization as in S1 (TS2) cannot be set and communication cannot be performed at all. An object of the present invention is to discontinue the method of detecting the pause determination time TW in an asynchronous data communication method using radio waves and add a notice signal as a predetermined synchronization signal to the head of a unit communication text. Therefore, it is an object of the present invention to provide a method capable of ensuring synchronization and communication between a parent station and a slave station even in an environment with noisy surroundings.

[Means for solving problems]

In order to solve the above-mentioned problems, the method of the present invention uses a character (1 or the like) consisting of a start bit (10a or the like), a data bit (10b or the like), a stop bit or the like of a predetermined length between the master station and the slave station. Is defined as a unit communication text (10, etc.) by connecting a predetermined number of times at a predetermined time interval, and a radio signal (hereinafter referred to as a unit communication text radio signal) that has been subjected to predetermined modulation using the digital signal of this unit communication text is an undefined time. In a synchronization method for detecting a start time point of the unit communication text radio signal in asynchronous data communication transmitted and received at intervals, a modulated radio wave corresponding to a logical value of the start bit is at least a time longer than the character length (such as TH), A continuous first notice radio wave signal (such as a notice radio wave of the notice H signal 301) and a modulated radio wave corresponding to a logical value opposite to the logical value of the start bit are transmitted to the first notice radio signal. Predetermined interval (T
L, etc.) and a second notice radio wave signal (such as a notice radio wave of the notice L signal) that is continuous and follows the first notice radio wave signal is added to the head of the unit communication text radio signal,
In the master station and the slave station, the first notice radio signal and the second notice radio signal are sampled by sampling signals at fixed time intervals, and there is a second notice radio signal subsequent to the first notice radio signal. It is characterized in that the start bit is detected when the start bit is continuous a predetermined number of times.

[Action]

Since the present invention communicates between a parent station and a child station, the parent station adds a notice signal having a predetermined structure as a signal for synchronization to the head of data (unit communication text) and transmits the data to the child station. Make a call. The slave station constantly monitors a signal received from the outside, and communicates by finding the above-mentioned notice signal from among the signals. Even if the external noise is generated periodically, when the interrogation signal having the warning signal at the head is received, the strength level of the interrogation signal can be communicated in advance with the S / N ratio. As long as it is selected so as to obtain, the interrogation signal is prioritized due to the masking phenomenon, and the noise becomes unnoticeable. Therefore, the start bit of the unit communication text can be easily discriminated and communication can be secured.

【Example】

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows a received demodulated signal of a slave station according to the present invention (see FIG.
The timings of (1)) and the synchronization detection operation ((2) in the same figure) are shown in comparison with the timing of the synchronization detection operation ((3) in the same figure) of the conventional slave station. In the state where the signal (noise 21) from the outside in the same figure (1) is received, the slave station makes a data determination 24 of this noise 21 as shown in the same figure (2), and a warning signal 30 (described later) as a synchronization signal. ), It returns to the warning signal waiting state. In this case, the warning signal detection time,
(That is, the time of the data determination 24) A short TD is a method for improving the performance of the system of the present invention. If the cycle of noise becomes shorter and the warning signal detection time TD or less is reached, the next signal may be input while the signal is being received and the warning signal 30 is being determined.
This is because there is a time lag in the detection of the warning signal 30 and it becomes impossible to detect the warning signal 30. When the slave station receives the interrogation signal 11 while waiting for the advance notice signal, the CPU of the slave station detects and receives the advance notice signal 30 at the beginning of the interrogation signal 11 as indicated by 25 in FIG. Go to processing. Here, the interrogation signal 11 has a structure in which a notice signal 30 as described later is added to the head portion of the unit communication message signal 10 described above. Generally, as a characteristic of a receiver, when two or more types of signals are being received, if there is a received signal that is larger than the rest of the received signals by a certain percentage or more, signals below the level of that signal will be received. There is a phenomenon of masking that does not happen. In this case, by receiving the interrogation signal 11 having a larger power than the noise 21, a reception output with the noise 21 masked can be obtained. Separately from this, even when an AGC (automatic gain control) circuit for keeping the output signal of the receiving amplifier constant, the noise signal is suppressed by adjusting the gain of the amplifier to the peak of the interrogation signal larger than the noise. can do.
However, these are effective when the level of the interrogation reception signal is larger than the noise level. As described with reference to FIG. 5, in the conventional method for detecting a non-signal state for a certain period of time (that is, the method for detecting the pause determination time TW), the timer is started from the time when the response signal 12 from another slave station ends. Then, if there is no noise 21, the reception (call waiting) mode is set after the pause determination time TW.
When it receives 21,21A, it starts the timer each time and tries to shift to the reception mode after the pause determination time TW after the noise disappears. However, when noise 21,21A, etc. are repeatedly received in a short cycle as shown in Fig. 5 (1) and Fig. 2 (1), the slave station can shift to the reception mode as shown in Fig. 2 (3). Disappear. Here, FIG. 2 (3) shows that the slave station is still in the detection mode of the pause determination time TW. FIG. 1 (1) is an enlarged view of the noise 21 and the interrogation signal 11 in the reception demodulated signal of the slave station according to the present invention, and FIG. 1 (2) shows the sampling timing of the CPU of the slave station at this time. Show. The advance notice signal 30 in the interrogation signal 11 is the unit communication message signal 10 described above.
Is added to the beginning of the. The advance notice signal 30 is the same as the logical value (in this case, "H") of the start bit 10a of the character in the unit communication message signal 10 (however, only the first part of the signal 10 is shown in this example). Logic (“H”)
Then, the notice H signal 301 having a time length TH that is at least longer than the character length, and the notice L signal having a logical value (“L”) obtained by inverting the logical value following this signal 30 and having a predetermined time length TL.
It consists of 302. The CPU in the slave station checks the received input signal again several tens of microseconds after the noise 21 is received by sampling the received signal input as shown in FIG. "H" is continuously detected at a certain number of sampling times (for example, 10 to 20 times) at the notice H signal 301 portion, and then at a certain number of times (at least 5 to 10 times or less) at the notice L signal 302 portion. ) When "L" is detected, synchronization is achieved by a method of detecting the start bit 10a at the head of the unit communication message signal 10. In the above embodiments, the configuration of the interrogation signal 11 of the master station has been mainly described, but it goes without saying that the notice signal 30 is provided at the head of the response signal 12 of the slave station in the present invention. Nor.

【The invention's effect】

In the present invention, between a master station and a slave station, a predetermined number of characters each consisting of a start bit, a stop bit, etc. are connected at a predetermined time interval to form a unit communication text, and a digital signal of this unit communication text is used. The start bit in the synchronization method for detecting the start time of the unit communication text radio signal in asynchronous data communication in which a radio signal that has been subjected to predetermined modulation (hereinafter referred to as unit communication text radio signal) is transmitted and received at indefinite time intervals. Of the first radio wave signal corresponding to the logical value of the start bit and the first radio wave signal corresponding to the logical value opposite to the logical value of the start bit. The signal has been maintained for a predetermined time different from the advance notice radio signal, and the first
And a second notice radio signal following the notice radio signal are added to the beginning of the unit communication sentence radio signal, and the first notice radio signal and the second notice radio signal are sampled at fixed time intervals in the master station and the slave station. And the start bit is detected when the second advance notice radio signal and the second advance notice radio signal are consecutive for a predetermined number of times. Even if one of the sampling signals overlaps with the noise, if the noise does not overlap continuously after the sampling signal, it is possible to distinguish between the noise and the warning signal, making it easy and reliable even in a noisy environment. It is possible to synchronize the sending and receiving stations.

[Brief description of drawings]

FIG. 1 is a time chart showing an essential configuration of a communication station as an embodiment of the present invention, and FIG. 2 is a time chart comparing the reception station of a slave station and its operation between the present invention and a conventional one. Three
FIG. 5 to FIG. 5 are time charts for explaining the conventional asynchronous communication. 1: character, 10: unit communication message signal, 10a: start bit, 10b: data bit, 11: interrogation signal, 12: response signal, 30: notice signal, 301: notice H signal, 302: notice L signal, TH , TL: time length.

Claims (1)

[Claims] 1. A unit communication text comprising a predetermined number of characters each having a start bit, a stop bit, etc., each having a predetermined length between a master station and a slave station at predetermined time intervals to form a unit communication text, and a digital signal of the unit communication text is used. The start bit in the synchronization method for detecting the start time of the unit communication text radio signal in asynchronous data communication in which a radio signal that has been subjected to predetermined modulation (hereinafter referred to as unit communication text radio signal) is transmitted and received at indefinite time intervals. Of the first radio wave signal corresponding to the logical value of the start bit and the first radio wave signal corresponding to the logical value opposite to the logical value of the start bit. A second notice radio signal that continues for a predetermined time different from the notice radio signal and that follows the first notice radio signal, and the head part of the unit communication text radio signal. In addition, the first notice radio signal and the second notice radio signal are sampled by sampling signals at fixed time intervals in the master station and the slave station, and the second notice radio signal follows the first notice radio signal. A method for synchronizing asynchronous data communication, characterized in that a start bit is detected when each of them continues for a certain number of times.