JPH04157938A - Communication error check method in communication system - Google Patents

Abstract

PURPOSE:To simplify the communication processing and to reduce the cost of a receiver by adopting a system such that plural data are sent in the synchronizing system and the occurrence of a communication error is discriminated when the count time from the start of reception to its end exceeds a timeout time. CONSTITUTION:At first when a start bit is received, the acceptance of reception is started and a data 1 is inputted to a receiver 15. When a stop bit is received, whether or not stop bits are consecutive is discriminated, a data 2 is inputted when not consecutive. Thus, after the input of a data 4, when stop bits are consecutive, the reception is terminated. A time is counted by a watchdog timer 17 up to this process and when the count of the timer 17 is interrupted till the timer 17 expires, it is discriminated that the communication is normally implemented. When the timer 17 expires before the count is stopped, error processing is implemented by a communication processing section 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting communication errors in an asynchronous data communication system.

[Background technology] FIG. 3 shows data transmission waveforms in the start-stop synchronization method.

In an asynchronous data communication system, a start bit (start signal) is used to signal the beginning of a 1-byte data signal (for example, 1-byte character data), and a stop bit (stop signal) is sent after the data signal. The addition signals the end of a 1-byte data signal. Then, by continuously transmitting a 1-byte data signal sandwiched between a start bit and a stop bit, multiple bytes of data are transmitted from the sending side to the receiving side, and when the stop bit continues, it is determined that communication has ended. . For example, FIG.
and data transmission waveforms when transmitting data 4.

However, when transmitting multiple bytes of data signals continuously using this start-stop synchronization method, communication may be interrupted midway due to an abnormality on the sending or receiving side, noise intrusion into the transmission line, short circuit between transmission lines, etc. may be done. Furthermore, communication may be started by mistaking noise as a start bit.

In order to detect such communication errors, conventionally, time-out determination processing is performed for each start bit and stop bit. The flowchart in FIG. 4 shows a conventional reception and timeout determination processing routine. Let's explain the case of transmitting a 4-byte data signal according to this flowchart. First, to explain the normal operation, when the receiving side receives a start bit, reception starts (S41), and data 1 is read into the receiving side (S42). The timer is then reset to 1=0 (S43) and it is checked whether a stop bit has been received (S44). If the stop bits are received, it is determined whether the reception has ended by checking whether the stop bits are consecutive (845).

If reception has not finished, the timer is reset to 1=0 (S46), and then it is checked whether a start bit has been received (S41). If the start bit has been received, data 2 is read into the receiving side (S42). Thereafter, steps 43 to 46 and steps 41 to 42 are similarly repeated twice to read data 3 and data 4. When data 4 is read in step 42, reception of stop bits is confirmed (S43.44), and if it is determined that the stop bits are consecutive and reception is complete (845), reception is terminated.

Conventionally, for such a normal reception operation, a timeout determination process is performed every time for each start bit and stop bit. That is, in step 46, the timer is set to 1=
After resetting to 0, it is checked whether the start bit has been received (S41), and if the start bit has not been received, it is necessary to judge whether the timer count has reached the specified timeout period and timed out. 547)
If the start bit is received before the timeout, it is determined to be normal and the flow continues normally. On the other hand, if the timeout period is reached without receiving the start bit, it is determined that the timeout has occurred, and an error handling routine is executed (S49). therefore,
If the communication is interrupted after receiving the stop bit, the timeout period will be reached before the start bit is received, and a communication error will be determined and the communication will be forcibly terminated. Furthermore, when each stop bit is received, a timeout determination process is performed in step 48 in the same way as when a start bit is received, and if it is determined that a timeout has occurred, an error handling routine is executed (849).

[Problems to be Solved by the Invention] However, when performing communication of multiple bytes in the l direction, if a communication error occurs even for 1 byte of data, that communication will be canceled. Unlike timeout determination processing, it is not necessary to perform timeout determination processing every time for each start bit and stop bit, and conventional timeout processing is complicated and redundant.

The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and its purpose is to provide a simple timeout determination processing method in an asynchronous data communication system.

[Means for Solving the Problems] The communication error detection method in the communication system of the present invention is as follows:
In a communication system that transmits multiple pieces of data using an asynchronous method, the time from the start to the end of reception of multiple pieces of data is counted by a timer, and the time measured by the timer from the start to the end of reception exceeds the timeout period. The system is characterized in that it sometimes determines that a communication error has occurred.

[Operations] In the present invention, the timeout determination process is not performed every time a start bit and stop bit are received, but rather the timeout determination process is performed by monitoring the time from the start of reception to the end of reception.

Therefore, timeout determination processing is performed only once for one communication, making it possible to omit unnecessary timeout determination processing, and to improve timeout determination processing in start-stop synchronization communication systems. Can be concise.

As a result, communication processing becomes extremely simple, reducing the storage capacity of ROM, etc. in the receiving device, reducing the cost of the receiving device, and improving the reliability of start-stop synchronization communication systems. be able to.

[Example code] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Figure 2 shows the configuration of the receiving side. This is a superimposed two-wire system that sends data signals using power lines, etc., and a drop-in line 1 branched from transmission lines 11a and llb such as power lines.
2a and 12b are provided with a transformer 13, and a receiving device 15 is connected to the transformer 13 via a pulse conversion circuit 14. The pulse conversion circuit 14 also includes a communication error processing section 1 for performing timeout processing.
6 is connected, and the communication error processing section 1G is equipped with a monitoring timer 17.

Therefore, the power waveform carrying the frequency-modulated (or amplitude-modulated) analog data signal is transferred to the transmission lines 11a, l.
lb (then only the AC signal passes through the transformer 13 and is sent to the receiving side. This AC signal is divided into electric power and an analog signal, and the analog data signal is sent to the third pulse converter circuit 14. The data is converted into a pulse signal as shown in the figure.The data converted into the pulse signal (digital signal) is sequentially inputted to the receiving device 15 by the start-stop synchronization method according to the processing routine shown in FIG. 1(a).

The data 1 in FIG. 3 is sent to this receiving device 15. The process for inputting data 2, data 3, and data 4 will be explained according to the flowchart of FIG. 1(a).

First, when a start bit is received, reception is started (S21), and data 1 is input to the receiving device 15 (S22). Next, it is checked whether or not a stop bit has been received, and a waiting state is entered until the stop bit is received (S23). When stop bits are received, it is determined whether the reception has ended based on whether the stop bits are consecutive or not (524). If the start bit has not been received, a waiting state is entered until the start bit is received (S25). Upon receiving the start bit, data 2 is input to the receiving device 15 (S22). Similarly, steps 23 to 25 and step 22 are repeated to input data 3 and data 4 to the receiving device 15. After inputting data 4, if it is determined in step 23 that stop bits have been received, it is checked in step 24 whether or not the stop bits are consecutive, and if the stop bits are consecutive, reception is terminated. In a similar manner, data of an arbitrary number of bytes is input to the receiving device 15 while synchronizing with the start bit and stop bit.

The monitoring routine for timeout determination processing in this reception system is provided independently of the data reception processing routine, and the monitoring timer 17 is configured to monitor the first start bit reception (first start bit reception) in the data communication processing routine.
Counting is started in synchronization with step 821) in FIG. 1(a), and when it is determined in the data communication processing routine that reception has ended (step 824 in FIG. 1(a)), counting is stopped. The timeout monitoring routine is executed in the communication error processing section 16 according to the procedure shown in FIG. 1(b).

When the monitoring timer 17 is cleared and starts counting in synchronization with the reception of the start bit (S31), the reception processing routine is finished and a determination is made as to whether or not the counting of the monitoring timer 17 has been stopped (S32). It is repeatedly and alternately checked whether or not the monitoring timer 17 has counted up (S33) when the timeout period has been reached. When the count of the monitoring timer 17 is stopped before the monitoring timer 17 times out, it is determined that the communication has not been interrupted and the communication has been performed normally,
The monitoring routine also ends. On the other hand, for example, if we consider a case where a start bit or the like is no longer received in a communication processing routine and communication is interrupted, in this case the monitoring timer 17 reaches the timeout time before the monitoring timer 17 stops counting. When the monitoring timer 17 times out in this way, a communication error handling routine is executed (S34), and an interrupt is made to the communication processing routine to forcibly terminate the communication processing routine.

In the timeout determination processing of the present invention, as described above, the timeout monitoring routine is made independent of the communication processing routine, and the monitoring timer is used to collectively monitor the communication from start to end. The processing can be simplified compared to .

Note that this method can also be applied to sequence control. In other words, a possible method is to provide a separate sequence monitoring routine and monitor the sequences all at once, without detecting the cause of the sequence interruption within the sequence.

[Effects of the Invention] According to the present invention, timeout determination processing is performed only once for one communication, and unnecessary timeout determination processing can be omitted. Accordingly, the timeout determination process in the communication system using the above method can be simplified.

As a result, communication processing becomes extremely simple, the storage capacity of the ROM etc. of the receiving device can be reduced, the cost of the receiving device can be reduced, and the reliability of the start-stop synchronization type communication system can be improved. can.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are flowcharts showing a routine for data reception and a routine for timeout determination processing in an embodiment of the present invention, and FIG. 2 shows the configuration of the receiving side of the same. A schematic configuration diagram, FIG. 3 is a diagram showing a data transmission waveform of an asynchronous method, and FIG. 4 is a flowchart showing processing in a conventional communication system. Patent applicant: Noritz Co., Ltd. Agent: Masafusa Nakano, patent attorney

Claims (1)

[Claims] (1) In a communication system that transmits multiple data using an asynchronous method, a timer counts the time from the start to the end of receiving multiple data, and the time measured by the timer from the start to the end of reception is the timeout period. A communication error detection method in a communication system that determines that a communication error has occurred when a