JPH09130382A - Polling communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a polling wait time by placing priority depending on kinds of each slave and data and causing contention through different delay times. SOLUTION: In the case of sending data from a slave 60 to a master 50, the master 50 sends a data packet C including information to inform start of contention to the slave 60. The slave 60 having data to be sent to the master 50 monitors its own reception port while awaiting a transmission opportunity for a prescribed delay time depending on the priority generated in itself at random. Then only a slave having no data to receive its own reception port generates at random its own preamble data D for the delay time generated in itself at random and sends the data to the master 50 and the master 50 sends the same preamble data E. The slave 60 compares the received preamble data E with the preamble data D sent by itself and sends a data packet F going to be sent when they are identical to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication method, and more particularly to a polling communication method capable of reducing polling time.

[0002]

2. Description of the Related Art Conventionally, an individual polling method has been mainly used to communicate between one device (hereinafter, master) that requests polling and a large number of devices (hereinafter, slaves) that respond to polling. That is, each slave has its own unique address number, and has the right to transmit / receive data when its own address data is received from the master according to a predetermined protocol. Master is Figure 1
As shown in, polling is sequentially performed with each slave in the determined order. In FIG. 1, M is the master and Sn is the nth slave. T indicates the time it takes for the master to poll one slave.

In such an individual polling communication method, the master transmits the address of the slave to be polled, and each slave receives the address and gives the transmission right to receive the data only when its own address is received. To be At this time, when the number of slaves connected to one master is large, the total polling time also increases and the data transmission time increases. In addition, since the number of communication devices that perform polling is fixed programmatically and lacks flexibility and expandability, each slave should respond to the master polling signal even when there is no data to send, so data transmission The presence of many polling signals and response signals on the road has a disadvantage of increasing noise sources for other information channels.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the generation of noise sources on a communication line and shorten the communication standby time.
It is to provide a polling communication method which is excellent in flexibility and expandability.

[0005]

In order to achieve the above-mentioned object of the present invention, in a polling communication method for performing polling communication between at least one master and a large number of slaves, the master starts a conflict. The first step of transmitting a data packet including information to notify the plurality of slaves, and when the slave has data to be transmitted, the slave randomly determines a predetermined priority according to the information to notify the start of the conflict. If there is no data received from other slaves during the delay time of, the second stage of transmitting its own preamble data,
The third step in which the master receives the preamble data and retransmits the preamble data, and the slave compares the preamble data transmitted by itself with the received preamble data and tries to transmit the same data packet. Is transmitted to the master.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic diagram for explaining a transmitting / receiving circuit of a master and each slave. In FIG. 2, member number 10 is a microprocessor, 20 is a modulation / demodulation unit, 30 is a transmission frequency setting unit, and 40 is a reception frequency setting unit. A half-duplex communication system in which data transmitted by the master can be received only by the slave and data transmitted by the slave can be received only by the master because the frequencies transmitted and received by the master and the slave are different from each other will be described as an example.

Data to be transmitted by the microprocessor 10 is input to the modulation / demodulation unit 20 through the transmission port TX, and the modulation / demodulation unit 20 modulates this data at the transmission frequency set by the transmission frequency setting unit 30 and then outputs it on the transmission line. To do. On the other hand, data input from another communication device through the transmission path is input to the modulation / demodulation unit 20, and the modulation / demodulation unit 20 demodulates the input data to the reception frequency set by the reception frequency setting unit 40 and demodulated data. Is output to the reception port RX of the microprocessor 10.

Both the master and the slave have such a transceiver circuit, but the transmission frequency of the master should be set as the reception frequency of the slave, and the reception frequency of the master should be set as the transmission frequency of the slave. At this time, the modulation / demodulation unit 20 may be configured using an ASK (amplitude shift keying) or FSK (frequency shift keying) modem. However, when the master and slave are far apart, when using the ASK modem, the size of the ASK modulated signal should be set large in order to make the transmission successful. When the size of the transmitted signal increases,
The input filter cannot sufficiently remove noise in an undesired frequency band. After all, when using an ASK modem using two different frequencies, the same phenomenon as using one frequency appears. Therefore, if the FSK modem is used, unlike the ASK modem, even when the master and the slave are far apart, it is not necessary to set the transmission signal size to be large, and the FSK modem is more resistant to noise.

FIG. 3 is a diagram for schematically explaining a polling communication method according to an embodiment of the present invention, and FIG. 4 is a waveform diagram of data transmitted and received between a master and a slave. First, a method of transmitting data from the master 50 to the slave 60 will be described with reference to FIGS. 3 and 4. When there is data to be transmitted by the master 50, the master 50 transmits the data packet A to the slave 60. At this time, the data packet A includes at least information notifying that it is the transmission data of the master and the unique address of the slave to be transmitted (1).

In the case where the received address in the slave 60 corresponds to its own unique address, in the case of normal reception, the ACK reception response B is transmitted to the master 50 within a predetermined time (2), and a reception error occurs. If so, NAK message B indicating a reception error is transmitted to the master 50 (2). The master 50 restarts from the process (1) of retransmitting the data packet A when a message indicating a reception error is received or no response is received.

A method of transmitting data from the slave 60 to the master 50 will be described below with reference to FIGS. 3 and 5. The master 50 sends a data packet C containing information indicating the beginning of the conflict to the slave 60 (3). When there is data to be transmitted to the master 50, the slave 60 monitors its receiving port while waiting for a transmission opportunity for a predetermined delay time due to the randomly generated priority. At this time, if there is data to be received at the receiving port RX of itself for a predetermined delay time, it means that another slave with a higher priority than itself has acquired the transmission right. It is postponed to and remains as a reception state. In this case, the delay time has a relatively small delay time when the priority is high, and the delay time is relatively long when the priority is low. Therefore, slaves with higher priority are given priority for transmission.

Only the slave that has no data received by its receiving port during the randomly generated delay time randomly generates its own preamble data D and transmits it to the master 50 (4). When the master 50 receives the preamble data D within a predetermined time, the master 50 also transmits the same preamble data E. At this time, if the preamble data D is not received within a predetermined time, the process is repeated from the above step (3) (5).

The slave transmitting the preamble data D in the slave 60 compares the received preamble data E with the preamble data D transmitted by itself, and if the slave preamble data D is the same, it means that the slave is authorized to transmit. The data packet F to be transmitted is transmitted (6). If, after transmitting the preamble data D, the received data E is not the same, it defers its transmission to the next opportunity and remains in the reception state (6).

The master 50 transmits an ACK reception response G when the data packet F from the slave is normally received, and transmits a NAK message G for notifying the reception error for retransmission when a reception error occurs (7). The format of the data packet transmitted / received between the master and the slave will be described below with reference to FIGS. 6 and 7.

In FIG. 6, PRE indicates preamble data that is present in the data packet transmitted from the master but not present in the data packet transmitted from the slave, CC indicates a control code, and DA / SA indicates reception. The master address has already been determined and can be omitted because it indicates the processing address and the transmission address, so in the case of a transmission data packet of a slave, the master address DA (destination address) of the reception process is omitted and the slave address SA (source address)
Is recorded, and in the case of the master transmission data packet, the slave SA is recorded. At this time, the master address DA of the transmission source is omitted. Inf indicates the information to be transmitted, BC indicates the number of bytes in the Inf field, and FCC indicates the frame check code, which is used for error checking at the receiving end.

FIG. 7 shows the structure of one character in a data packet, where ST is a start bit and SP.
Is a stop bit, b _{0 to} b ₇ are data bits, and P is a parity bit. One character consists of 11 bits in total. At this time, P is used as an even or odd parity bit for error detection, and can also be used as a bit for determining the reception mode. Explaining this, the reception side can use P to specify the reception mode to determine whether data can be received. That is, when the reception mode is 1, the reception can be performed only when the parity bit of the received character is 1, and when the reception mode is 0, the reception can be performed regardless of the parity bit.

This will be described in detail with reference to FIG. In FIG. 8, the master sends a data packet a signaling the start of a conflict, and since the data packet a should be received by all slaves, the parity bit P = 1 is set. At this time, the reception mode of each slave should be set to 1. Next, the slave having the data packet to be transmitted waits for the given random delay time, then transmits the preamble data b, sets the reception mode to 0, and waits for the next reception. At this time, since only the master receives the preamble data b, the parity bit P is used as a parity bit for error detection as it is. Next, the master transmits the preamble data c, and the parity bit P of this preamble data c is set to 0. Therefore, since only the slave that has transmitted the preamble data b has the reception mode of 0, data reception is possible. Then, the data packet d to be transmitted is transmitted from the slave to the master, and the master transmits a reception response e. At this time, since the reception response e needs to be received only by the slave, the parity bit P is set to 0.

Next, when there is a data packet to be transmitted from the master to the slave, the master transmits the data packet f. At this time, as shown in FIG. 9, in the data packet f, PRE, CC and DA / SA should be received by all the slaves, so that the parity bit P is set to 1
, BC, Inf, and FCC need only be received by the corresponding slave, so the parity bit P is set to 0. That is, each slave sets the receive mode to 0 only when DA / SA is the same as its own address, and BC, Inf, and FCC are set.
To be received. Therefore, unnecessary reception operations can be reduced and communication efficiency can be improved.

The delay time depending on the priority of each slave will be described in more detail. In order to solve the problem of delay in transmission time due to data collision that occurs when polling communication is performed, contention will be performed according to priority. That is,
Each slave obtains the transmission right during the delay time given by itself unless there is data to be transmitted from other slaves having priorities. At this time, the delay time indicates the time from the reception of the data indicating the start of contention from the master to the transmission of its own preamble data by each slave, and is for preventing data collision.

Further, the data is given a priority according to the nature of the data to be transmitted and received. For example, when the data types are classified into emergency data, general data, and net management data as shown in the following table, the priority order is as follows.

[0021]

[Table 1]

As can be seen from the above table, the basic delay time is made different depending on the priority order of the data to be transmitted, and the random delay time is made different according to the priority order given randomly by each slave. In order to prevent mutual collision, the delay range of each data is adjusted differently. At this time, when the number of slaves is 9, the range of the randomly generated delay time is (0 to 8) x 3UT (unit time), and when there are 4 types of data, it is (0 to 3) x 3UT. Become. Further, if the delay time according to the type of data is uniformly determined regardless of the number of times of data transmission, it becomes one factor of the delay of the transmission time.
Generally, general data has a large number of data transmissions and relatively small number of net management data. Therefore, in order to reduce the minimum communication period, when the data packet indicating the start of competition is transmitted from the master, if the information about the data type is included, only the data of the corresponding type can be transmitted and received. That is, when the master sends a data packet including information indicating the start of conflict and information indicating emergency data as information for the type of data,
Only slaves that try to send emergency data participate in the race, slaves that try to send other types of data are excluded from the race.

As described above, the master can flexibly use the data depending on the type of data and the number of transmissions and receptions to reduce the transmission time.
10, 11 and 12 and 13 are flowcharts of polling communication of each master and slave according to an embodiment of the polling communication method according to the present invention.

In FIGS. 10 and 11, in step 100, the master determines whether there is transmission data to be transmitted to the slave. In step 110, a data packet is transmitted if there is transmission data. At this time, in the data packet
PRE, CC, DA / SA are set to parity bit P = 1 for each character so that they are received by all slaves, and BC, Inf, and FCC need only receive the corresponding slaves, so parity bit for each character. P is set to 0. Then, in step 120, if the master receives a reception response ACK indicating a normal reception, the transmission is completed or the data packet is retransmitted. In step 130, if there is no data to be transmitted in step 100, the master transmits a data packet including information indicating the start of contention, step 140 determines whether preamble data PRE can be received from the slave, and step 150 receives the preamble data PRE. Case Retransmit the same preamble data PRE to the slave. Next, in step 160, the data packet from the slave is received, in step 170, it is determined whether or not a reception error occurs, and in step 180, a reception response ACK is transmitted in the case of normal reception, or in step 190, the reception error is transmitted. Carry message NAK to inform.

In FIGS. 12 and 13, first, in step 200, each slave sets the reception mode to 1, and in step 210, preamble data PRE is received. At this time, 2
In step 20, it is determined whether the preamble data PRE includes information indicating the start of contention. If it does not include it, CC and DA / SA in the data packet are received in step 230. At this time, since all the reception modes are set to 1 in step 240, whether the reception is possible or not is determined by the setting state of the parity bit P. Each slave compares its own address with that of DA / SA, and sets the reception mode to 0 in step 250 and waits for the next reception. If the address is different, it starts again from step 200. Next, in step 260, depending on the setting state of the parity bit P, only the corresponding slave is BC, Inf from the master.
, FCC is received, and in step 270, 280-step reception response ACK or 290-step reception error message NAK is transmitted to the master depending on whether normal reception is possible or not. At this time, 30
In step 0, if the information indicating the start of contention is included in step 220, each slave determines whether there is transmission data to be transmitted to the master, and if there is transmission data in step 310, it is randomly given by each slave. During the delay time PLT according to the priority, it is determined in step 320 whether there is received data. In step 330, if there is no received data during PLT, preamble data PRE is transmitted, and
In step 0, if the preamble data PRE that is the same as the transmitted preamble data PRE is received, the remaining CC, BC, Inf and FCC of the data packet are transmitted in step 350. If the reception response ACK indicating the normal reception is received from the master, the transmission is completed.
Repeat the steps.

[0026]

As described above, the polling communication method according to the present invention can reduce the polling waiting time by giving priority to each slave according to the type of data and competing for different delay times due to the priorities. Further, by giving only slaves having data to be transmitted to polling communication, the generation of noise sources on the communication line is reduced, and there is an advantage that it can be easily expanded by changing the program of the master when the hardware is changed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional individual polling communication method.

FIG. 2 is a configuration block diagram of a transmission / reception circuit unit of a master and a slave.

FIG. 3 is a diagram schematically showing an embodiment of a polling communication method according to the present invention.

FIG. 4 is a waveform diagram of data transmitted and received between a master and a slave.

FIG. 5 is a waveform diagram of data transmitted and received between a master and a slave.

FIG. 6 is a diagram showing a data packet transmitted / received between a master and a slave.

FIG. 7 is a diagram for explaining a configuration of each character of the data packet of FIG.

8 is a diagram for explaining a transmission / reception operation depending on a setting state of a parity bit in each character of FIG. 7.

9 is a diagram for explaining a transmission / reception operation depending on a setting state of a parity bit in each character of FIG. 7.

FIG. 10 is a flowchart illustrating an embodiment of a polling communication method according to the present invention.

11 is a flowchart following FIG.

FIG. 12 is a flowchart for explaining an embodiment of a polling communication method according to the present invention.

FIG. 13 is a flowchart following FIG.

[Explanation of symbols]

 10 microprocessor 20 modulation / demodulation unit 30 transmission frequency setting unit 40 reception frequency setting unit 50 master 60 slave

Claims (5)

[Claims] 1. A polling communication method for performing polling communication between at least one master and a plurality of slaves, wherein the master transmits a data packet including information indicating the start of contention to the plurality of slaves. 1 step, when there is data to be transmitted by the slave, data received from other slaves etc. during a predetermined delay time according to a priority given randomly according to the information indicating the start of the contention. Otherwise, the second step of transmitting its own preamble data, the third step of receiving the preamble data by the master and retransmitting the preamble data, and the slave transmitting the preamble data of its own and the received preamble data. Data packets that are to be transmitted if they are the same. Polling communication method characterized by comprising a fourth step of transmitting to over. 2. When the master has a data packet to be transmitted to the slave, it transmits a data packet including at least information notifying that it is its own transmission and a reception address, and uses the same unique address as the reception address. The polling communication method according to claim 1, further comprising the step of: a slave having the data packet. 3. The polling communication method according to claim 1, wherein the data packet includes at least a control code, a transmission / reception address, information data, the number of bytes of information data, and a frame check code. 4. A parity bit is included in each character of the data packet, and each parity bit is used as an original error check bit and a bit that determines whether reception is possible or not. Polling communication method. 5. The polling communication method according to claim 1, wherein the priority is given in accordance with the type of data in the two steps, and the basic delay time is determined by the priority.