JPH07131467A - Polling resending device - Google Patents

Abstract

PURPOSE:To provide the polling resending device which can efficiently transfer data to other slave stations by shortening the time required for retransmission by polling. CONSTITUTION:This device includes one group of transmission lines, plural stations (6, 7, and 8) which are connected to the transmission lines and can freely send response data including messages indicating the length of data according to a supplied polling signal, and a main station (1) which are connected in multidrop form to the respective stations through the transmission lines, and calculates the time required to receive the response data based on the message of the received response data when sending the polling signal to the respective station and receiving the response data from each station, but resends the polling signal to the stations according to the calculated reception required time when not receiving the response data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polling retransmission device, and more particularly to a polling retransmission device for data transfer between a master station and a plurality of dependent stations connected in a multi-drop format.

[0002]

2. Description of the Related Art A general example will be described with reference to the drawings.

FIG. 11 is a block diagram for explaining the multi-drop format, and FIG. 12 is a polling sequence diagram showing a general data transmission / reception state at the time of retransmission in a data transfer system between a master station and a slave station. is there.

As shown in FIG. 11, the master station 10 and a plurality of slave stations 11 to 13 are connected to a set of transmission lines in a multi-drop manner, and the master station sends a polling signal () to each slave station. Downlink signal) is transmitted and response data (uplink signal) from the dependent station is received.

Here, in the case where the main station cannot obtain a response from each subordinate station, as shown in FIG. 12, no response is obtained after a time sufficiently longer than the time required from the downlink to the uplink of the data. The polling signal is retransmitted to the dependent station. In FIG. 12, T0 indicates that the timer has expired,
× indicates that the response from the dependent station has disappeared.

[0006]

In the general polling retransmission method, when the response from the subordinate station is not obtained for some reason, the main station retransmits to the subordinate station, but the timer expires. When setting the value for the first time, it is necessary to set a sufficiently long time compared to the time until the response data is received in response to polling, so if it continues as it is, retransmission will start. However, when the system is rebuilt by increasing or decreasing the number of dependent stations, the timer expiration value that was set up to that point will not be updated. There was a problem that it was not appropriate for the system, which hindered the original data transfer.

An object of the present invention is to provide a polling / retransmission device which can reduce the time required for polling retransmission and can efficiently perform data transfer to other subordinate stations.

[0008]

A plurality of transmission lines, which are connected to the transmission lines and are capable of transmitting response data including a message indicating the length of data according to a polling signal supplied thereto. Is connected to each station in a multi-drop format via a set of transmission lines, and when a polling signal is sent to each station and response data is received from the station, a response is sent based on the received response data message. It is characterized by including a main station for calculating a data reception required time and retransmitting a polling signal to the station according to the calculated reception required time when no response data is received from the station.

[0009]

According to the polling signal supplied from a plurality of stations connected to one set of transmission lines, response data including a message indicating the length of the data can be transmitted freely, and the main station can transmit via one set of transmission lines. When a polling signal is sent to each station and response data is received from the station, the response data reception time is calculated based on the received response data message and the station responds. If no data is received, the polling signal is retransmitted to the station according to the calculated reception time, so the time required to start retransmission of the polling signal can be shortened.
Data can be efficiently transferred to each station.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the polling retransmission device of the present invention is a system in which a master station and a plurality of slave stations are connected in a set of transmission lines in a multi-drop manner, and the master station operates for each slave station. In the polling method of transmitting a polling signal (downstream signal) and receiving response data (upstream signal) from the dependent station, the dependent station indicates the length of the response data in the response data to the polling signal from the master station. By adding the message, the master station calculates the reception time of the response data from the slave station from the transmission speeds of the master station and the slave stations that are already known and the message indicating the length of the response data. The above problem can be solved by setting the timer expiration value to a value slightly larger than the receiving station time.

That is, between a main station and a plurality of subordinate stations connected to the main station in a multi-drop format on a set of transmission lines, polling is performed from the main station, and each subordinate station transmits response data to the polling. In the return polling response method, the dependent station adds a message indicating the length of the response data confidence to the response data to the master station, so that the master station uses the message for receiving the response data. By calculating the time, the master station transmits a polling signal to the dependent station, and when the response data from the dependent station cannot be received, or when the number of dependent stations is increased or decreased, the reception The polling retransmission apparatus is characterized in that the main station is provided with means for setting a required time to a timer expiration value.

This embodiment will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a polling retransmission device of the present invention.

In FIG. 1, reference numeral 1 is a main station, which comprises an input / output processing unit 2, a memory 3, a timer management unit 4, and a communication control unit 5. N subordinate stations are connected in parallel to the main station 1, 6 is a subordinate station 1, 7 is a subordinate station 2, and 8 is a subordinate station n.

Next, the operation of each of the above components will be described.
When the subordinate station 1, the subordinate station 2, ... Dependent station n receives the polling signal from the master station 1, the subordinate station 1 can obtain the transmission right until all the transmissions are completed. That is, the dependent station 1, the dependent station 2, ... The dependent station n must not transmit to the master station 1 until it receives the polling signal from the master station 1.

The communication control unit 5 is connected via the input / output processing unit 2 to
When normal response data is received from one subordinate station, the process shifts to polling processing for the next subordinate station. The communication control unit 5 also adds a message indicating the length of the response data itself, which is added to the response data from the dependent station as shown in FIG. 10 described later, and the transmission rate of the predetermined transmission line. Then, the time required for receiving the response data is calculated, and the value is recorded in the memory 3. The communication control unit 5 also transmits a timer expiration value change request to the timer management unit 4. The input / output processing unit 2 transmits the polling signal sent from the communication control unit 5 to the subordinate station via the transmission path, and the response data returned from the subordinate station to the communication control unit 5.
Further, the input / output processing unit 2 transmits a timer start request and a timer stop request to the timer management unit 4. The memory 3 records the reception time of the response data from the subordinate station transmitted from the communication control unit 5, and the timer management unit 4 refers to it as the timer expiration value.

The timer management unit 4 receives the timer start request and the timer stop request from the input / output processing unit 2, and after receiving the timer start request, receives the timer stop request from the input / output processing unit 2 within a specified time. If not, the timer expiration notification is transmitted to the communication control unit 5. Further, when the timer expiration value change request is received from the communication control unit 5, the timer expiration value for the dependent station is changed.

Next, the processing in the input / output processing unit 2, the timer management unit 4 and the communication control unit 5 shown in FIG.

FIG. 2 is a diagram showing the state transition of the communication control unit 5,
3 is a flow chart showing the processing in the first state of the communication control unit 5, FIG. 4 is a flow chart showing the processing in the second state of the communication control unit 5, and FIG. 5 is a processing in the third state of the communication control unit 5. FIG. 6 is a flowchart showing the process of the communication control unit 5 in the fourth state.

As shown in FIG. 2, the communication control unit 5 is provided with four states of "idle state α", "timer expiration value setting state β", "data transmission / reception state γ", and "timer recovery state δ". I will provide it.

As an example of the transition of each state, when there is a condition of R / T at the time of transition from the α state to the β state, “When the signal of R is received in the α state, the signal of T is transmitted. Transition to the β state. ”

The processing in each state will be described below with reference to the drawings.

The "idle state α" shown in FIG. 3 represents a state in which nothing is done, and the communication control unit 5 receives a polling signal transmission request from the upper module (step 3-1) and sends a polling signal to the subordinate station. (Step 3-
2) After resetting the timer expiration value to the initial value (step 3-3), the timer expiration value is newly set.
Transition to "timer expiration value setting state β" (step 3)
-4, see A in FIG. 2).

"Timer expiration value setting state β" shown in FIG.
Indicates a state in which a timer expiration value for a dependent station is newly or again set, and the timer expiration value is processed with an initial value. When the communication control unit 5 receives the response data from the dependent station via the input / output processing unit 2 (Step 4-2) while waiting for the received data from the dependent station (Step 4-1), the response data By referring to the message in the message indicating the length of the response data itself, the time required for reception is calculated from the transmission rate of the transmission line and the length of the response data (step 4-4), and the time is set as the dependent station. Memory for each 3
(Step 4-5), and the polling signal is transmitted to the dependent station via the input / output processing unit 2 (step 4-).
6). Although details will be described later, in step 4-5, the longer time is compared with the previously recorded time, and the longer time is recorded. Further, the communication control unit 5 determines whether polling of the dependent station for several rounds has been completed (step 4-
7) If it is determined that the processing has ended, the maximum value is extracted from the reception time for each subordinate station, that value is set as the timer expiration value, and a request to change the timer expiration value is sent to the timer management unit 4. After that (step 4-9), the state transits to the “data transmission / reception state γ” (step 4-10, see transition B in FIG. 2).

In step 4-1, when the received data is not awaited, a signal indicating a timer expiration notification is received from the timer management section 4 (step 4-3), and the dependent stations for which no response data is obtained are received. And retransmit (step 4-8).

"Data transmission / reception state γ" shown in FIG. 5 represents a state in which data is transmitted / received to / from the subordinate station, and when the communication control unit 5 is in a state of waiting for reception data from the subordinate station (step 5-1). ), The response data from the subordinate station is received via the input / output processing unit 2 (step 5-2), and the polling signal is transmitted to the next subordinate station via the input / output processing unit 2 (step 5-). 3). If not waiting for received data, a signal indicating a timer expiration notification is received from the timer management unit 4 (step 5-4) and retransmitted to the dependent station for which response data was not obtained (step 5). -5),
Transition to "timer recovery state δ" (step 5-6, see transition C in FIG. 2).

The "timer recovery state δ" shown in FIG. 6 represents a state in which retransmission is repeated to a dependent station for which no response has been obtained,
When the communication control unit 5 receives the response data from the dependent station via the input / output processing unit 2 (step 6-1) while waiting for the received data from the dependent station (step 6-2), the input / output processing unit 2 A polling signal is transmitted to the subordinate station via (step 6-3), and the state transits to "data transmission / reception state γ" (step 6-4, see transition D in FIG. 2). If the received data is not in a waiting state, a signal indicating a timer expiration notification is received from the timer management unit 4 (step 6-5),
In order to confirm the reproducibility, the communication control unit 5 judges whether or not the specified number of times of retransmission has been performed (step 6-6), and when the specified number of times has been executed, it is judged that "the timer has expired because of a long message". Then, in order to set the timer expiration value again, after resetting the timer expiration value to the initial value (step 6-8), the state transits to "timer expiration value setting state β" (step 6-9, FIG. 2). See transition E). If it has not been performed the specified number of times, it is retransmitted to the dependent station for which response data was not obtained (step 6-7).

Next, the procedure by which the communication control unit 5 rewrites the timer expiration value for each subordinate station in the memory 3 will be described with reference to FIG.

FIG. 7 is a diagram showing a procedure for recording the timer expiration value in the memory.

In the "timer expiration value setting state β" described above, the communication control unit 5 refers to the table in the memory 3 in which the timer expiration values of the subordinate stations are recorded, and compares the previously recorded value with the newly recorded value. Compare with the value obtained by calculation. Figure 7
Then, as an example, the case of dependent station 1 and dependent station 2 is shown.
Since the value obtained by the dependent station 1 is smaller than the value recorded last time, the table is not rewritten. On the contrary, in the case of the dependent station 2, since the obtained value is larger, the table is rewritten. In the case of this example, the rewritten value represents the maximum value in the receiving time, so that value is set as the timer expiration value. When the timer expires due to a long message, it is possible to deal with it by changing the timer expiration value in this way.

Next, the processing of the input / output processing unit 2 shown in FIG. 1 will be described with reference to the flowchart of FIG.

FIG. 8 is a flow chart showing the processing of the input / output processing unit 2 in FIG.

When the input / output processing unit 2 receives a polling signal transmission from the communication control unit 5 to the subordinate station while waiting for a message from the subordinate station (step 8-1), A polling signal is transmitted to the subordinate station via the transmission line (step 8-3), and then a signal indicating a timer activation request is generated to the timer management unit 4 (step 8-4). In step 8-1, when the response data is received from the dependent station via the transmission line (step 8-5), the timer management unit 4 sends a signal indicating the timer stop request.
To the communication control unit 5 (step 8-7).

Next, the processing of the timer management unit 4 shown in FIG. 1 will be described with reference to the flowchart of FIG.

FIG. 9 is a flowchart showing the processing of the timer management unit 4 in FIG.

When the timer management section 4 waits for received data from the input / output processing section 2 (step 9-1) and receives a timer start request from the input / output processing section 2 (step 9-2), it starts the timer. It is activated (step 9-3).
In addition, the timer management unit 4 (step 9-
4) When the timer stop request is received from the input / output processing unit 2 within the predetermined time, the timer is stopped (step 9-5). If the timer stop request is not received from the input / output processing unit 2 within the predetermined time in Step 9-4, the timer expiration notification is transmitted to the communication control unit 5 (Step 9-8). Further, in step 9-1, when the signal indicating the timer expiration change request is received from the communication control unit 5 (step 9-6), the memory 3 is referred to as shown in FIG. The value is changed as the timer expiration value for the dependent station (step 9-7).

FIG. 10 is a diagram showing an example of a data message format.

The message format of data exchanged between the master station and the slave stations will be described with reference to FIG.

A "message identifier" indicating the type of message is added to the beginning of each message, and in the case of response data, "length" indicating the length of the message.
Data is added after “h” after the “message identifier”. The communication control unit 5 uses the "len"
It is possible to recognize the length of the response data by referring to “gth”.

As described above, according to the present embodiment, the timer expiration value is made smaller than the initial value in accordance with the length of the response data from the subordinate station, so that for some reason the response data from the subordinate station should occur. Even when is lost, data can be efficiently transferred to other dependent stations without lowering polling efficiency.

[0041]

EFFECTS OF THE INVENTION Response data including a message indicating the length of data can be freely transmitted in accordance with a polling signal supplied from a plurality of stations connected to one set of transmission lines, and a main station can form one set of transmission lines. When the station is connected to each station in a multi-drop format via a polling signal and the response data is received from the station, the required reception time of the response data is calculated based on the received response data message. If no response data is received from, the polling signal is retransmitted to the station according to the calculated time required for reception.
The time required to start retransmission of the polling signal can be shortened, and data transfer can be efficiently performed to each station.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a polling retransmission device of the present invention.

FIG. 2 is a diagram showing a state transition of a communication control unit.

FIG. 3 is a flowchart showing processing in a first state of a communication control unit.

FIG. 4 is a flowchart showing processing in a second state of the communication control unit.

FIG. 5 is a flowchart showing processing in a third state of the communication control unit.

FIG. 6 is a flowchart showing processing in a fourth state of the communication control unit.

FIG. 7 is a diagram showing a procedure for recording a timer expiration value in a memory.

FIG. 8 is a flowchart showing processing of an input / output processing unit.

FIG. 9 is a flowchart showing processing of a timer management unit.

FIG. 10 is a diagram showing an example of a message format.

FIG. 11 is a block diagram illustrating a multi-drop format.

FIG. 12 shows a data transfer method between a master station and a slave station,
FIG. 7 is a polling sequence diagram showing a data transmission / reception state during general retransmission.

[Explanation of symbols]

 1 main station 2 input / output processing unit 3 memory 4 timer management unit 5 communication control unit 6, 7, 8 dependent station

Claims (1)

[Claims] 1. A set of transmission lines, and a plurality of stations connected to the set of transmission lines and capable of transmitting response data including a message indicating a length of data according to a polling signal supplied thereto. It is connected to each station in the multi-drop format via the one set of transmission lines, and when the polling signal is transmitted to each station and the response data is received from the station, the response data is received based on the received response data message. A polling retransmission device comprising: a main station that calculates a required time and, when no response data is received from the station, retransmits a polling signal to the station according to the calculated required reception time.