JP3280852B2 - Polling communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] 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 for communication between a device (hereinafter, a master) requesting polling and a plurality of devices (hereinafter, slaves) responding to polling. That is, each slave has its own unique address number, and has the right to transmit and receive data when receiving its own address data from the master according to a predetermined protocol. Master, Figure 1
As shown in (1), polling is sequentially performed with each slave in a predetermined order. In FIG. 1, M indicates a master and Sn indicates an n-th slave. T indicates the time it takes for the master to poll one slave.

[0003] In such an individual polling communication system, the master transmits the address of the slave to be polled, and each slave receives the address and gives the transmission authority to receive data only when its own address is received. Can be At this time, when the number of slaves connected to one master is large, the overall polling time is also increased and the data transmission time is increased. In addition, the number of communication devices to be polled is fixed programmatically, and the flexibility and expandability are not enough.Even if each slave has no data to transmit, it must respond to the master's polling signal, so data transmission There is a disadvantage in that the presence of many polling signals and response signals on the road increases noise sources for other information channels.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the occurrence of noise sources on a communication line, 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 or more masters and a number of slaves, the master starts a conflict. A first step of transmitting a data packet including information to be notified to the plurality of slaves, and when the slave has data to be transmitted, after receiving the information indicating the start of the conflict, at least the type of data and transmission / reception of data are performed. A second step of transmitting own preamble data if there is no data received from another slave or the like during a predetermined delay time according to the priority given by one of the frequencies, and a step in which the master receives the preamble data. A third step of retransmitting the preamble data, wherein the slave transmits its transmitted preamble data If the result of comparison between the received preamble data is the same, seen including a fourth step of transmitting a data packet to be transmitted to the master, the
The data packet sent from master to slave is
Whether reception at the slave is set for each data item
And said that you are.

[0006]

FIG. 2 is a schematic diagram for explaining a transmitting / receiving circuit of a master and each slave. 2, reference numeral 10 denotes a microprocessor, 20 denotes a modulation / demodulation unit, 30 denotes a transmission frequency setting unit, and 40 denotes a reception frequency setting unit. The half-duplex communication system in which data transmitted by the master and received by the master at different frequencies can be received only by the slave and data transmitted by the slave can be received only by the master will be described.

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

[0008] Although both the master and the slave have such a transmitting and receiving circuit, the transmitting frequency of the master should be set as the receiving frequency of the slave, and the receiving frequency of the master should be set as the transmitting frequency of the slave. In this case, the modem unit 20 may be configured using an ASK (amplitude shift keying) or FSK (frequency shift keying) modem. However, when the ASK modem is used when the master and the slave are far apart, the size of the ASK modulation signal should be set large 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. As a result, when using an ASK modem using two different frequencies, the same phenomenon as when 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, the transmission signal does not need to be set large, and the transmission signal is more resistant to noise.

FIG. 3 is a diagram schematically illustrating 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. If 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 indicating that the data is transmission data of the master and a unique address of a slave to be transmitted (1).

[0010] The slave 60 whose received address corresponds to its own unique address transmits an ACK reception response B to the master 50 within a predetermined time in the case of normal reception (2), and a reception error occurs. If so, a NAK message B indicating a reception error is transmitted to the master 50 (2). The master 50 restarts from the step (1) of retransmitting the data packet A when the message indicating the reception error is received or there is no response.

Next, a method of transmitting data from the slave 60 to the master 50 will be described with reference to FIGS. The master 50 transmits a data packet C including information indicating the start of the contention to the slave 60 (3). When there is data to be transmitted to the master 50, the slave 60 monitors its own receiving port while waiting for a transmission opportunity for a predetermined delay time according to a priority generated at random. At this time, if there is data received at its own receiving port RX for a predetermined delay time, it means that another slave with a higher priority than itself has acquired the transmission right, so that And it remains in the receiving state. At this time, the delay time is relatively small when the priority is high, and the delay time is relatively long when the priority is low. Accordingly, slaves with higher priorities are given priority for transmission.

Only the slave having no data received at its own receiving port during the delay time generated at random by itself generates its own preamble data D at random and transmits it to the master 50 (4). The master 50 transmits the same preamble data E again when the preamble data D is received within a predetermined time. At this time, if the preamble data D is not received within a predetermined time, the process is repeated from the above (3) (5).

The slave 60 that has transmitted the preamble data D among the slaves 60 compares the received preamble data E with the preamble data D transmitted by the slave 60, and if the preamble data D is identical, it means that the transmission right has been obtained, so that the slave 60 tries to transmit. The data packet F to be transmitted is transmitted (6). If the received data E is not the same after transmitting the preamble data D, the transmission is postponed to the next opportunity and remains in the reception state (6).

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

In FIG. 6, PRE indicates preamble data which is present in a data packet transmitted from the master but does not exist in a 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 processing address. In the case of a slave transmission data packet, the master address DA (destination address) of the reception processing is omitted and the slave address SA (source address) is omitted.
Is recorded, and in the case of the master transmission data packet, the slave SA is recorded, and at this time, the master address DA of the transmission source is omitted. Inf indicates information to be transmitted, BC indicates the number of bytes in the Inf field, and FCC indicates a 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, SP
Shows stop bit, b ₀ ~b ₇ data bits, P is a parity bit respectively. One character is composed of a total of 11 bits. 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 a reception mode. To explain this, the receiving side can determine whether data can be received by designating the receiving mode using P. That is, when the reception mode is 1, reception is enabled only when the parity bit of the reception character is 1, and when the reception mode is 0, reception is enabled regardless of the parity bit.

This will be described in detail with reference to FIG. In FIG. 8, the master transmits a data packet a indicating the start of the conflict, and the data packet a is set to the parity bit P = 1 since the data packet a should be received by all slaves. At this time, the reception mode of each slave should be set to 1. Next, after a certain slave of the data packet to be transmitted waits for a given random delay time, it 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 originally intended. Next, the master transmits the preamble data c, and the parity bit P of the preamble data c is set to 0. Therefore, only the slave that transmitted the preamble data b has the reception mode of 0, so that data reception is possible. Next, 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, the data packet f has the parity bit P set to 1 because PRE, CC and DA / SA should be received by all slaves.
And the parity bit P is set to 0 since BC, Inf and FCC only need to be received by the corresponding slave. That is, each slave sets the reception mode to 0 only when the DA / SA is the same as its own address, and sets BC, Inf and FCC.
Is received. Therefore, unnecessary reception operations can be reduced, and communication efficiency can be improved.

The delay time according to the priority of each slave will be described in more detail. In order to solve the problem of transmission time delay caused by data collision occurring during polling communication, contention is performed according to priority. That is,
Each slave obtains the transmission authority if there is no transmission data from another slave preceding the priority during the delay time given by the priority. At this time, the delay time indicates the time from when data indicating the start of contention from the master is received by each slave to when its own preamble data is transmitted, in order to prevent data collision.

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

[0021]

[Table 1]

As can be seen from the above table, the basic delay time is made different according to the priority of data to be transmitted, and the random delay time is made different according to the priority randomly assigned by each slave. The delay range of each data is adjusted differently to prevent mutual collision. At this time, if the number of slaves is 9, the range of the randomly generated delay time is (0-8) × 3UT (unit time), and if there are four types of data, (0-3) × 3UT. Become. In addition, if the delay time according to the type of data is determined uniformly regardless of the number of times of data transmission, this is one factor of the delay of the transmission time.
In general, general data has a large number of data transmissions and a relatively small number of network management data. Therefore, when transmitting a data packet indicating the start of contention from the master to reduce the minimum communication period, if information on the type of data is included, only data of the corresponding type can be transmitted and received. That is, when the master sends a data packet including information indicating emergency data as information on the type of data along with information indicating the start of contention,
Only slaves trying to send emergency data participate in the conflict, and slaves trying to send other types of data are excluded from the conflict.

As described above, the master can extend and reduce the transmission time depending on the type of data and the number of times of transmission / reception.
FIG. 10, FIG. 11, FIG. 12, and FIG. 13 show flowcharts of polling communication between each master and slave according to one embodiment of the above-described 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, if there is transmission data, a data packet is transmitted. At this time, the data packet
PRE, CC, DA / SA are set to the parity bit P = 1 of each character so that they are received by all slaves, and then BC, Inf, and FCC are parity bits of each character since only the corresponding slave needs to be received. P = 0 is set. Next, in step 120, if the master receives a reception acknowledgment indicating normal reception, the transmission is completed, or the data packet is retransmitted. In step 130, if there is no transmission data in step 100, the master transmits a data packet including information indicating the start of contention. In step 140, it is determined whether the preamble data PRE can be received from the slave. In this case, the same preamble data PRE is retransmitted to the slave. Next, in step 160, a data packet from the slave is received. In step 170, it is determined whether a reception error has occurred. In step 180, a reception response ACK is transmitted in the case of normal reception, or in step 190, a reception error is detected. Transmit the message NAK to inform.

Referring to FIGS. 12 and 13, first, at step 200, each slave sets the reception mode to 1, and at step 210, the 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 not, in step 230, CC and DA / SA in the data packet are received. At this time, since all the reception modes are set to 1 in step 240, whether or not reception is possible is determined according to the setting state of the parity bit P. Each slave sets its reception mode to 0 at step 250 if the DA / SA and its own address are the same, and waits for the next reception. If the address is different, the process is repeated from step 200. Next, at step 260, only the slave is changed from the master to BC or Inf according to the setting state of the parity bit P.
, FCC is received, and in step 270, a ACK reception response ACK or a 290 step reception error message NAK is transmitted to the master depending on whether or not normal reception is possible. At this time, 30
In step 0, if 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 order, it is determined in step 320 whether there is received data. At step 330, if there is no received data during the PLT, the preamble data PRE is transmitted.
In step 0, if the preamble data PRE identical to the transmitted preamble data PRE is received, in step 350, the remaining CC, BC, Inf, and FCC of the data packet are transmitted. If a reception response ACK indicating 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 reduces the polling waiting time by giving priority to each slave according to the type of data and competing with different delay times. In addition, there is an advantage that the generation of noise sources on the communication line is reduced by providing only the slave having data to be transmitted to the polling communication, and the hardware can be easily expanded through a change in the master program 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 illustrating 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 data packets transmitted and 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. 6;

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

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

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

FIG. 11 is a flowchart following FIG. 10;

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

FIG. 13 is a flowchart following FIG. 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Microprocessor 20 Modulation / demodulation part 30 Transmission frequency setting part 40 Receiving frequency setting part 50 Master 60 Slave

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-188161 (JP, A) JP-A-56-47147 (JP, A) JP-A-8-70307 (JP, A) JP-A 5- 63722 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 12/28-12/46

Claims (4)

(57) [Claims] 1. A polling communication method for performing polling communication between at least one or more masters and a plurality of slaves, the master transmitting a data packet including information indicating a start of contention to the plurality of slaves. The first step is that, when there is data to be transmitted, the slave receives information notifying the start of the contention, and after a predetermined delay time according to a priority given by at least one of data type and data transmission / reception frequency. A second step of transmitting its own preamble data if there is no data received from another slave or the like; a third step of receiving the preamble data by the master and retransmitting it; The comparison result between the transmitted preamble data and the received preamble data is the same If, viewed contains a fourth step of transmitting a data packet to be transmitted to the master, the data packet transmitted from the master to the slave
Indicates whether reception at the slave is enabled or disabled for each data item.
Polling communication method characterized by being performed . 2. When the master has a data packet to be transmitted to the slave, the master transmits at least a data packet including a reception address and information indicating the transmission of the data packet, and transmits the same unique address as the reception address. 2. The polling communication method according to claim 1, further comprising receiving the data packet by a slave having the same. 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 the information data, and a frame check code. 4. The data packet according to claim 3, wherein each character of the data packet includes a parity bit, and each parity bit is used as an original error check bit and a bit for determining whether or not reception is possible. Polling communication method.