JP2560657B2 - Multiplexer - Google Patents

Description

The present invention relates to a multiplex transmission apparatus in which a primary station and a plurality of secondary stations are bus-connected in a multi-drop manner by a two-core dedicated line.

(B) Conventional Technique In the above-mentioned multiplex transmission device, as a technique for detecting a transmission abnormality, the number of occurrences of abnormality of each terminal, that is, the secondary station is accumulated, and the transmission abnormality occurs only after a certain number of consecutive occurrences. By operating the pushbutton switch, etc., a command for testing the line is transmitted, and the response is confirmed by the answerback method to determine whether there is a transmission error. A short circuit test is performed every time it is transmitted to each terminal. Etc. are adopted.

(C) Problems to be Solved by the Invention However, in the above-mentioned first method, there is a problem that it is necessary to wait for the accumulation of abnormalities and it takes time to detect the abnormality. There is a problem that it requires a special operation of pressing the button of, and in the second method, for each short circuit test,
There has been a problem that the processing time becomes long and therefore the transmission time becomes long.

The present invention was made by paying attention to the above problems, and when all the connected terminals are all unresponsive,
It is an object of the present invention to provide a transmission device that can detect an abnormality in a transmission line promptly by performing a short-circuit test without requiring a special operation and yet increasing the transmission time.

(D) Means and Actions for Solving Problems The multiplex transmission device of the present invention has a configuration in which a primary station and a plurality of secondary stations are connected to each other
A communication end detecting means for detecting the end of communication for a cycle, and a response confirming means for checking whether or not there is a response for all secondary stations connected until the end of communication.
When the response confirming means confirms that there is no response for all the connected secondary stations, it is provided with a short circuit examining means for examining the presence or absence of a short circuit in the transmission path.

In this multiplex transmission device, every time the communication of one cycle of the secondary station is completed, it is confirmed by the response confirmation means whether or not all the secondary stations are not responding, and it is confirmed that all the secondary stations are not responding. In this case, the short-circuit checking means moves to the short-circuit checking of the transmission line. Therefore, a short-circuit test is performed with one transmission to all stations. Further, since the short circuit test is performed under the condition that all secondary stations do not respond, the short circuit test of the transmission line is not performed during normal transmission. Therefore, the transmission time does not become long.

(E) Examples Hereinafter, the present invention will be described in more detail with reference to Examples.

FIG. 1 is a system block diagram of a multiplex transmission apparatus in which the present invention is implemented. This multiplex transmission device is a primary station 1
In addition, a plurality of secondary stations 2 _-1 , 2 _-2 , ..., 2 _-5 are bus-connected in a two-core dedicated transmission line 3 in a multi-drop manner. As shown in FIG. 2, the primary station 1 receives an MPU (microprocessor unit) 11 and transmission data TxD from this MPU 11.
A driver 12 for sending to the secondary station and a receiver 13 for receiving the received data RxD from the secondary station are provided. Here, a differential type is used as an example of the driver and the receiver. In addition, the transmitted data TxD is returned and the received data R
Since it has a configuration that can be captured in xD, it is possible to perform a sender check of transmitted data.

In this multiplex transmission device, normally, that is, in a normal state, the primary station sends time-sequential addresses to the respective secondary stations, transmits a command, and receives a response from the secondary station to this command. And short-circuit check is not performed. It is configured to perform a short circuit test when no response is obtained even after one cycle of command transmission from the primary station to the secondary station is completed.

Next, the transmission procedure of the above embodiment will be described with reference to the flow charts shown in FIGS. 3 (A) and 3 (B). The control operation according to this transmission procedure is executed by the MPU 11 of the primary station 1.

When the operation starts, first turn off the response terminal flag
Then, the cycle end flag is turned off [step ST (hereinafter abbreviated as ST) 1, ST2]. Here, the response terminal presence flag is set to ON when there is a response from the secondary station, that is, the terminal in response to the command from the primary station 1, that is, is set to "1", and is OFF when there is no response, that is, This flag is set to "0". The cycle end flag is turned on (= "1") when one cycle of communication with each secondary station is completed, and turned off (= "1") when communicating with a terminal in the middle of a cycle.
This flag is set to "0"). These flags are turned off in ST1 and ST2 for initialization.

Next, initialize the pointer for the operation table (ST
3). Here, the operation table stores the address code of each secondary station as shown in FIG. 4, and the operation table pointer stores and designates the address of the operation table. Subsequently, one byte of the start address of the operation table designated by the pointer is set as the station address (ST4). As a result, the secondary station 2 _-1 is designated first. Next, it is determined whether the station address is not 00 (ST5), but the cycle operation has just started, the station address is not 00, and the cycle end flag is turned ON.
It is determined whether or not (ST6). Cycle end flag is OFF
Since it is still being done, this judgment is also NO and jumps to ST7,
Enter frame transmission (ST7). The format of the frame is, as shown in FIG. 5, a station address Ad which is a code for designating a terminal, a command Cm which is a code for notifying the meaning of data, information (data) I and a frame error for detecting a frame error. Composed of code BBC.

After the frame is transmitted, it waits for a predetermined time until the reception interrupt (ST8, ST13). When there is a response from the secondary station 2 _-1 , it is determined whether the specified number of bytes has been received, and (ST
9) If YES, the error detection code returned
Check if the BBC is correct (ST10), and if correct,
The response terminal presence flag is turned on (ST11), the operation table pointer is incremented by 1 (ST12), and the process returns to ST4. Within a predetermined time
If there is no receive interrupt (ST13), the specified number of bytes is not received (ST9), or the BBC is incorrect (ST10),
Skip ST11 and add only operation table pointer to +1
Then (ST12), and again return to ST4.

In ST4, the secondary station 2 _-2 of the operation table is addressed by the pointer this time. Then, the same processing as that for transmitting the frame is advanced to the secondary station _2-1 . Thereafter, similarly, the pointer is incremented by 1, and the address of the operation table is designated to be forwarded.
Next station 2 _-3, 2 _-4, time sequentially in 2 _-5, frame transmission is performed. When the end address, which is the last address in the operation table, is specified, ST5 “station address ≠ 0
If "0""is NO, the cycle end flag is turned ON in ST14, the process returns to ST3, the operation table pointer is initialized again, and the start address of the operation table is designated again, and the station address is set to the secondary address. Set it as station 2 _-1 (ST4), so that the determination of "station address 00" in ST5 is YES, and "whether the cycle end flag is ON" is determined (ST6). Since the cycle end flag is turned on in ST6, the determination in ST6 is YES, and then it is determined whether or not the response terminal presence flag is OFF (ST15). In the cycle, it means that there was no response from all terminals, that is, the secondary station, and in this case, there is a possibility of short circuit of the transmission line 3. Therefore, a short circuit test is performed (ST16).

When the short-circuit test routine is entered, as shown in FIG. 3 (B), first, a short-circuit test code is transmitted (ST19), and a reception interrupt is waited for until a predetermined time elapses (ST20, ST22). . When a reception interrupt occurs, "Reception data =
Send data? "Is judged, and if a match is obtained, the process directly returns. If no match is obtained, or if the reception interrupt does not come in even after a lapse of a predetermined time (ST22),
Notify the transmission line short circuit error (ST23) and return.

When the short circuit test is completed, the response terminal flag is turned off (ST17), and the cycle end flag is turned off (ST1).
8) Go to ST7 frame transmission. In ST15,
If the response terminal flag is ON, the determination is NO and the short-circuit test is not required. Therefore, skip ST16 and ST17 and go to ST18.
Jump to, turn off the cycle end flag, and proceed to ST7 frame transmission.

When the above operation proceeds while the transmission is normally performed, as shown in FIG. 6, each command is transmitted as the transmission data TxD, and in response thereto, the response is received as the reception data RxD from the secondary station. Received, secondary station 2 _-1 , ...
The scan operation is repeated with one cycle of command transmission and response reception for 2 _-5 .

On the other hand, if a short circuit occurs in the transmission line, for example, as shown in FIG. 7, if a short circuit occurs at time t ₁ , then there is no response for the scan period of one cycle. In this case, following the end of the cycle with no response, a transmission line short circuit check is performed, and if a short circuit is determined, transmission is stopped and maintenance for short circuit release is performed during that period, for example at time t ₂ . When the short circuit is released, the transmission line short circuit check is performed again and it is confirmed that the short circuit has been released, and the next transmission scan operation starts.

(F) Effect of the Invention According to the present invention, the end of communication of one cycle of the secondary station, which is a transmission terminal, is detected, and each of the two during this cycle is detected.
Since the absence of response from the next station is detected and the short-circuit check of the transmission path is performed only when all the secondary stations have no response, the short-circuit check is not performed during normal transmission. You can avoid a long time. In addition, short-circuit detection can be performed with one data transmission to all secondary stations, there is no need to wait for continuous abnormality occurrence, and the time for short-circuit detection can be shortened. Moreover,
No special operation such as switch operation is required to detect a short circuit.

[Brief description of drawings]

FIG. 1 is a system block diagram of a multiplex transmission apparatus in which the present invention is implemented, FIG. 2 is a block diagram showing a schematic hardware configuration of a primary station of the multiplex transmission apparatus, and FIG. FIG. 3 (B) is a flowchart showing the transmission procedure of the multiplex transmission device.
FIG. 4 is a flow chart showing the details of the short circuit test routine of the same flow chart, FIG. 4 is a diagram showing an operation table of the multiplex transmission apparatus of the embodiment, and FIG. 5 is a format configuration of a transmission frame of the multiplex transmission apparatus. 6 and 6 are time charts showing transmission data and reception data for explaining the transmission state at the normal time, and FIG. 7 shows transmission data and reception data for explaining the transmission state at the time of occurrence of a short circuit. It is a time chart. 1: 1 primary station, 2 _-1 , 2 _-2 , ..., 2 _-5 : secondary station, 3: 2 dedicated line, 11: MPU.

Claims (1)

(57) [Claims] 1. In a multiplex transmission apparatus in which a primary station and a plurality of secondary stations are connected, a communication end detecting means for detecting the end of one cycle of communication of a secondary station which is a transmission terminal, and this communication. Until the end, when the response confirmation means for confirming the presence / absence of response for all connected secondary stations and the response confirmation means confirms that there is no response for all connected secondary stations. And a short-circuit checking means for checking whether or not there is a short-circuit in the transmission path.