JP2001024645A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a communication system of a simple structure capable of relieving the processing burden in a slave unit and simultaneously enhancing communication responsiveness. SOLUTION: This communication system is constituted by successively cascade connecting plural slave units 2 with a master unit 1 via a communication line 3, and each slave unit is provided with a control part 21 to generate response by deciding whether a request from a host unit is addressed to the present station. Then a direct response is realized by providing a switching means 26 to directly transmit the response to the request to the host unit, when the request is addressed to the present station, to transmit the request to a subordinate unit and to simultaneously transmit the response to be transmitted from the subordinate unit to the host unit as is, when the request is not addressed to the present station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system having a simple configuration suitable for use as, for example, a multi-point data sensing system, and particularly having improved communication responsiveness.

[0002]

2. Related Art Recently, a multipoint data sensing system that collects sensing information from sensors installed at a plurality of locations in a central management unit and controls and manages the entire information has been used in various fields. A communication system used as this type of sensing system generally performs addressing for a plurality of slave units connected to a master unit via a bus line, such as serial communication represented by RS485. , Each of which is configured to perform data communication between the addressed slave unit and the master unit.

However, in the communication system having the above configuration, it is necessary to set addresses for a plurality of slave units in advance, and it is necessary to consider a complicated communication procedure of specifying a slave unit by specifying an address. is necessary. On the other hand, a communication system has been proposed in which a plurality of slave units are sequentially cascade-connected to a master unit, and data communication is sequentially performed between adjacent units. According to such a communication system, it is possible to manage a plurality of slave units according to the order of cascade connection, and it is only necessary to manage and control communication between adjacent units. There are advantages such as a simple procedure.

[0004]

However, in a communication system in which a plurality of slave units are cascaded, each slave unit transmits data (request) sent from a higher-order unit to its own station. It is determined whether or not the received data is addressed to the own station. If the received data is not addressed to the own station, the received data is transmitted (transferred) to a lower slave unit. Similarly, it is determined whether the data (response) sent from the lower unit is addressed to the own station,
If the data is not addressed to the own station, the received data is transmitted (transferred) to a higher-order unit, thereby realizing data communication between adjacent units.

For this reason, it cannot be denied that it takes time for the master unit to receive a response to a request issued to a specific slave unit. In particular, it takes a great deal of time to receive a response from a cascade-connected lower slave unit, and there is a problem in terms of communication responsiveness. In addition, for a slave unit positioned halfway between the master unit and the slave unit specified by the master unit, data transfer between adjacent units must be controlled each time. There are also problems such as

The present invention has been made in view of such circumstances, and has as its object to realize efficient data communication with good communication responsiveness and reduced processing load on a slave unit on the way. It is an object of the present invention to provide a communication system having a simple configuration that can perform the above.

[0007]

In order to achieve the above object, a communication system according to the present invention comprises a plurality of slave units connected in cascade to a master unit. A communication control unit is provided for determining whether or not received data from the connected higher-level unit is data addressed to the own station, and generating transmission data based on the received data. Is switching means for controlling, wherein the transmission data is transmitted to a higher-order unit when the received data is data addressed to the own station, and the transmission is performed when the received data is not data addressed to the own station. Switching means for transmitting data to a lower unit and transmitting data transmitted from a lower unit to a higher unit without change is provided. It is characterized in that.

[0008] That is, the communication control unit in the communication system according to the present invention determines whether or not the received data from the higher-level unit is data addressed to the own station, and based on the determined result, based on the received data. The transmission data to be transferred to the lower order unit or the transmission data to be responded to the master unit is generated. The operation of the switching means is controlled in accordance with the result of the determination, and when the received data is data addressed to the own station, the transmission data is transmitted to a higher-order unit, while the received data is addressed to the own station. If not, the transmission data is transmitted to the lower unit, and the data transmitted from the lower unit is directly transmitted (transferred) to the higher unit. Then, a process of generating transmission data for an upper unit based on the reception data from the lower slave unit is omitted, thereby reducing the processing load,
It is characterized by improved communication responsiveness to the master unit.

A communication system according to the present invention is defined in claim 2.
As described in the above, each of the slave units includes a control terminal pulled up via a resistor, and a ground terminal connected to the control terminal of a cascaded higher-order unit, wherein the communication control unit Is characterized by comprising means for judging whether or not the own station is the lowest-order slave unit cascaded from the potential of the control terminal and controlling the operation of the switching means.

That is, the potential of the control terminal pulled up via a resistor is controlled by the control terminal and the ground terminal connected between adjacent slave units, whereby the lowest-order slave unit connected in cascade is connected. It is characterized by being able to easily determine whether or not the data is sent to the master unit without wasteful transmission of data from the lowest slave unit to the lower unit. And

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A communication system according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a communication system according to the present invention, where 1 is a master unit (MU), 2 (2a, 2b, 2
c,... 2n) communicate with the master unit 1 via the communication line 3.
Are a plurality (n) of slave units (SU) connected in cascade in order. Each of these slave units 2 (2a, 2b, 2c, to 2n) is, for example, # 0, # 1, # 2, to # (n- The address is uniquely set as 1). The communication line 3 includes, for example, a control line 3c, a data line 3d, and a clock signal line.

Each slave unit 2 is provided with a sensing element such as a photoelectric sensor or a magnetostrictive sensor, for example, to detect a state at a predetermined measurement (monitoring) target portion, and to provide the detected information, for example, It plays the role of notifying the master unit 1 as 1-bit slave information.
On the other hand, the master unit 1 has a role of collecting slave information detected by each of the slave units 2 and integrally managing the entire slave information (multi-sensing system).

Each slave unit 2 is, for example, shown in FIG.
Control unit (communication control unit) 21 including a CPU as shown in FIG.
And performs data communication with the master unit 1 according to a communication control procedure described later. The slave unit 2 has a storage unit (slave information) that stores, as slave information to be notified to the master unit 1, detection information detected by a sensing element (not shown) provided in the slave unit 2, for example, at predetermined intervals. A storage unit 22 is provided. The storage unit 22 is an EE which is an information storage medium capable of electrically erasing the storage information.
This is realized using a PROM or the like.

Each slave unit 2 receives, for example, a communication request (request), which is communication data issued from the master unit 1, via a higher-order unit cascade-connected to the master unit 1. A data receiving unit 23 for taking in the control unit 21 is provided.
The control unit 21 includes a determination unit 24 for determining whether or not the received data is addressed to the own station, as described later, and transfers the data to a lower unit based on the received data according to the determination result. It has a function of generating transmission data or transmission data to be responded to the master unit 1. The transmission data generated by the control unit 21 in this manner is output via the transmission unit 25 and transmitted to the lower slave unit or the upper unit via the switching unit 26.

The switching means 26 is functionally a first switch 26 for selectively outputting transmission data output from the transmission unit 25 to a lower unit as shown in FIG.
a, a second switch 26b that operates complementarily to the first switch 26a and outputs transmission data output from the transmission unit 25 to a higher-order unit, and a second switch 26b that is complementary to the second switch 26b. , That is, a third switch 26c for selectively outputting received data from a lower unit to an upper unit as it is in place of selecting the transmission data.

Such first to third switches 26a, 26a,
The operation of the switching unit 26 including the switches 26b and 26c is controlled by the control unit 21 described above, particularly in accordance with the determination result of the determination unit 24. Specifically, when the received data from the higher-level unit is destined for the own station, the switching unit 26 sets the switch state shown in FIG. 2 to disconnect the electrical connection with the lower-level unit, It functions to transmit the transmission data output from the transmission unit 25 to a higher-order unit. On the other hand, if the data received from the higher order unit is not addressed to the own station, the switching means 26 switches the first to third switches 26a and 26a.
b and 26c are switched in conjunction with each other to transmit the transmission data output from the transmission unit 25 to the lower unit and to transmit the data received from the lower unit to the higher unit. .

Each slave unit 2 basically configured as described above is further connected to a control terminal 28 pulled up to a power supply voltage Vcc via a resistor 27 and a control terminal 28 of a higher-order unit. And a ground terminal 29. The control terminal 28 and the ground terminal 29 are connected between a plurality of cascaded slave units 2a, 2b, to 2n as shown in FIG. Accordingly, in the upper slave unit 2 in which the slave units 2 are cascade-connected to the lower slave unit, the control terminal 2 is connected to the ground terminal 29 of the lower slave unit.
8 is set to the ground potential. On the other hand, the slave unit 2n connected at the lowest level is kept at the power supply voltage Vcc pulled up via the resistor 27 because the control terminal 28 is not grounded.

The control unit 21 determines from the potential of the control terminal 28 whether or not the slave unit 2 is cascaded at the lowest position in the communication system. Specifically, if the potential of the control terminal 28 is the ground potential (0), the control unit 21 determines that the next slave unit is connected to the lower level, and the potential of the control terminal 28 is the power supply voltage Vcc. , It is determined that the slave unit is the lowest-order slave unit in the communication system constructed by cascade connection. And the control unit 21
Controls the operation of the switching means 26 according to the determination result. Specifically, when it is determined that the slave unit is the lowest-order slave unit, the operation is forcibly controlled so that the transmission data from the transmission unit 25 is always transmitted to the higher-order unit.

Thus, a plurality of slave units 2 (2a, 2b,.
According to the communication system constructed by connecting n) in cascade, as shown in FIGS. 4A and 4B, a communication request (request) issued from the master unit 1 is first. If the request is for the slave unit 2a (# 0), the slave unit 2a (# 0) that has received the communication request (request) determines from the address information that it is addressed to its own station, and A response is generated as transmission data to notify the master unit 1 of the request. Then, the operation of the switching means 26 is controlled to transmit the transmission data to the master unit 1 as shown in FIG. Accordingly, in this case, no data is transmitted to the slave units 2b,..., 2n cascaded below the slave unit 2a (# 0).
Data from b, .about.2n is not transferred to the master unit 1.

On the other hand, if the communication request (request) issued from the master unit 1 is for the third-stage slave unit 2c (# 2), the first-stage slave that receives this communication request (request) Unit 2
The control unit 21 of a (# 0) determines from the address information that it is not addressed to its own station. Then, the received data is generated as transmission data to be notified to the next slave unit 2b (# 1), and this is generated as the next slave unit 2b (# 1).
(# 1). At the same time, the control unit 21 switches the operation mode of the switching unit 26 so that the data (response) sent from the next slave unit 2b (# 1) is transferred to the master unit 1 as it is.

Thus, the first-stage slave unit 2a
The control unit 21 of the second-stage slave unit 2b (# 1) receiving the communication request (request) from (# 0) judges the received data, and determines the first-stage slave unit 2a.
Similarly to (# 0), the transmission data is generated and transmitted to the next third-stage slave unit 2c (# 2). At the same time, the data (response) sent from the third-stage slave unit 2c (# 2)
The operation mode of the switching means 26 is switched so as to transfer the data to “a”.

Now, the third-stage slave unit 2c (#
In 2), the second-stage slave unit 2b (#
It receives the communication request (request) from 1) and knows that the communication request is addressed to its own station. As a result, the third-stage slave unit 2c (# 2) generates a response as a transmission data to notify the master unit 1 of the communication request (request), and activates the switching unit 26. Controlling upper slave unit 2b
(# 1). Then, the higher-order slave unit 2b (# 1) having received the response receives the above-mentioned response (response) as it is because the switching means 26 is set as described above. 0), and the slave unit 2a (# 0) similarly transfers the response to the master unit 1 as it is. As a result, as shown in FIG.
The response (response) issued from c (# 2) is transferred to the master unit 1 as it is through the upper slave units 2b and 2a in that order.

Therefore, according to the communication system for executing data communication between the master unit 1 and the plurality of slave units 2 as described above, each slave unit 2 transmits data received from an upper unit to its own station. The operation of the selecting means 26 is controlled depending on whether the data is not the slave unit or not, and if the data is not addressed to the own station, a communication request is transmitted to the lower unit if the data is not the slave unit. At the same time, it operates so as to transfer the response (response) from the lower unit to the higher unit as it is. When the communication request (request) is addressed to the own station, the corresponding response (response) is transmitted. Generate it and send it to the upper unit. Therefore, it is not necessary to control the data transmission to the higher-order unit while determining the data (response) received from the lower-order unit each time, so that the processing load can be greatly reduced. In addition, the master unit 1 is notified of the response (response) from the slave unit 2 of the request destination by passing through the intermediate slave unit 2 as it is, so that the response (response) can be obtained quickly. As a result, the communication responsiveness can be sufficiently improved.

Further, the slave unit 2n connected at the lowest position can recognize from the potential of the control terminal 28 that it is the lowest unit connected in cascade in the communication system. Then, even if the received data (communication request) from the upper unit is not addressed to the own station, it responds to the master unit 1 without transmitting the communication request to the lower unit.
Therefore, there is no waste of communication, and it is possible to avoid a problem of waiting for a response for a long time while issuing a communication request to a slave unit that does not exist for the master unit 1. Therefore, also in such a point, the communication responsiveness can be improved.

The above-described slave unit 2 is specifically configured as shown in FIG. 5, for example. In this case, the first switch 26a of the switching unit 26 is connected to the control unit 2
1 and is implemented as a gate circuit that operates in response to the control signal CNT from the first and second switches 26b, 26b,
26c is realized as a multiplexer (selector) that operates by receiving the control signal CNT as a selection signal. At the same time, by using the amplifying function of these gate circuits and multiplexers (selectors), the switching means 26 is configured to also function as the transmitting unit 25.

Next, a processing operation in the control unit 21 of each slave unit 2 for realizing the above-described communication procedure will be described with reference to FIGS. Slave unit 2
Is turned on, first, the initial processing shown in FIG. 6 is started, and the above-described second and third switches 26 are activated.
b, 26c, a multiplexer (selector)
The signal D-Rx sent from the lower order unit to the master unit 1 is set to pass directly, that is, the third switch 26c is set to conduct [Step S1].
Next, the gate circuit forming the first switch 26a is switched to O
N (state in which the first switch 26a is turned on) and data D-Tx to be sent to the lower unit
[Step S2]. That is, the selection means 2
6 is set to a state in which data can be sent to a lower unit, but is set to a state in which data is not actually sent and data from a lower unit is relayed to an upper unit.

In this state, the potential of the control terminal 28 is checked to determine whether or not the own station is the last (lowest) unit slave-connected to the master unit 1 (step S3). The potential of the control terminal 28 is equal to the power supply voltage V
If it is cc, it is determined that the slave unit is the lowest-order slave unit in the communication system constructed by cascade connection, and the final unit flag is set [Step S].
4]. If the potential of the control terminal 28 is the ground potential (0), the control unit 21 determines that the next slave unit is connected to the lower level, and clears the last unit flag [Step S5]. In this way, the control unit 21 determines the connection position of the own station in the communication system, sets / clears the final unit flag according to the determination result, ends the initial processing, and shifts to the normal processing shown in FIG. [Step S6].

In this steady processing, it is constantly monitored whether or not data (reception command) T-Dx is received from the upper unit via the reception unit 23 (step S11).
When the data T-Dx is not received, the multiplexer (selector) transfers the signal D-Rx sent from the lower unit to the master unit 1 as it is, that is, the third switch 26c is turned on. [Step S12]. At the same time the first switch 2
The gate circuit constituting 6a is turned on and there is no data D-Tx to be sent to the lower order unit [step S13], and the reception of data T-Dx is awaited.

When the data (reception command) T-Dx is received from the upper unit [Step S1]
1], the control unit 21 determines whether or not the destination address indicated by the data (reception command) T-Dx is larger than the address assigned to the own station in advance (the order of cascade connection with the master unit 1). I do. When the destination address is not larger than the own station address, in other words, the data (reception command) T-Dx of the destination address smaller than the own station address is not notified as described later. Is determined to be the data (reception command) T-Dx (step S15). In this case, command processing is performed on the data (received command) T-Dx, and predetermined response data T-Rx is created based on the data T-Dx [step S16].

Thereafter, the switching means 26 is switched to transfer the data from the lower unit (third switch 26).
c) as well as the data transmission path (first switch 26a) for the lower order unit [Step S1].
7], the response data T-Rx is returned to the host unit via the second switch 26b [Step S18]. That is, the communication line for the lower unit is disconnected, and the slave unit 2 directly returns a response (response) to the data (received command) T-Dx.

On the other hand, when the destination address is larger than the own station address [Step S14], it is determined that the data is not data addressed to the own station. In this case, it is determined whether the flag is set or cleared by referring to the last unit flag described above [Step S20]. That is, it is checked whether the own station is the lowest-order slave unit 2 or not. When the final unit flag is cleared, the gate circuit forming the first switch 26a is turned on (the first switch 26a is turned on), and the third circuit forming the multiplexer is turned on. The switch 26c is turned on to set a state in which data from the lower unit is relayed to the upper unit [Step S21]. Thereafter, the above-mentioned data (reception command) T-Dx is transmitted as data to be transmitted to the lower slave unit via the first switch 26a (gate circuit). In other words, in this case, the data T-Dx from the master unit 1 is relayed to the lower unit, and the data T-Rx from the lower unit is simply transferred to the upper unit. .

On the other hand, if the final unit flag is set [Step S20] even though the destination address indicated by the received data T-Dx is larger than the own station address [Step S14], this is regarded as abnormal. to decide. That is, since the master unit 1 designates a slave unit 2 lower than the own station even though the own station is the lowest slave unit 2, this is determined to be abnormal [step S23]. In this case, the switching means 26 is switched to cut off the data transfer path from the lower unit (third switch 26c) and to transmit the data to the lower unit (first switch 26c).
a) is cut off [Step S24], and the second switch 26 is turned off.
The response data T-Rx indicating the abnormality is returned to the upper unit via b (step S25). That is, since the own station is the lowest-order slave unit 2, the own station promptly returns an abnormal response without transferring the received data T-Dx downward.

The switching means 2 thus operates as described above.
6 (first to third switches 26a, 26b, 26c), promptly returns a response to the received data (request) addressed to the own station, and returns the received data (request) to itself. If the received data (request) is not addressed to the station, the slave is configured to transfer the received data (request) to the lower slave unit and to transfer the response (response) sent from the lower slave unit to the higher unit as it is. According to the communication system configured by cascading the units 2, the master unit 1
If the slave unit 2 accessed from
The response is returned directly to the master unit 1 while sequentially passing through the upper slave unit 2. In other words, the slave unit 2 accessed from the master unit 1 can apparently directly respond to the master unit 1. Therefore, the communication responsiveness can be sufficiently improved.

In addition, in the slave unit 2 connected above the slave unit 2 that responds to the request, the transfer of the data is controlled while determining the destination of the received data (response) from the lower slave unit 2 each time. Since there is no need to perform this operation, that is, since the received data (response) from the lower slave unit 2 is simply transferred to the upper unit, the processing load can be greatly reduced.

Further, as described above, the self-determination is made as to whether or not the slave unit is the lowest-order slave unit, and a response is promptly made to an abnormal access from the master unit 1. And the communication efficiency can be improved. Further, effects such as very simple control in each slave unit 2 and a simple overall system configuration can be obtained.

The present invention is not limited to the above embodiment. For example, the number of slave units 2 that form a communication system by cascade connection may be determined according to system specifications such as the processing capability of the master unit 1. In short, various modifications can be made without departing from the scope of the invention.

[0037]

As described above, according to the present invention, a plurality of slave units cascaded to a master unit promptly respond to the master unit for received data addressed to the own station. When the data is not the data addressed to the own station, the received data is transferred to the lower slave unit, and the response from the lower slave unit is simply transferred to the upper unit as it is. Can respond directly to the master unit, and its communication responsiveness can be improved. In addition, since it is not necessary to determine the destination of the response data each time and control the data transfer, it is possible to greatly reduce the processing load on each slave unit.

Furthermore, since it is possible to self-determine whether or not the slave unit is connected to the lowest order and quickly respond to an abnormal access, time-out management or the like for response reception in the master unit is unnecessary. Also in this respect, there can be obtained an effect that the communication responsiveness can be improved. Therefore, information can be easily and efficiently transmitted under a simple system configuration, and a great effect in practical use such as being suitable for a multipoint data sensing system can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a slave unit in the communication system shown in FIG. 1;

FIG. 3 is a diagram schematically illustrating a concept of a data communication form of the communication system illustrated in FIG. 1;

FIG. 4 is a diagram showing the concept of the lowest determination in each slave unit.

FIG. 5 is a diagram showing a specific configuration example of a slave unit.

FIG. 6 is a diagram showing a procedure of initial processing in data communication control executed in the slave unit.

FIG. 7 is a diagram showing a procedure of response control in data communication control executed in the slave unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Master unit 2 Slave unit 3 Communication line 21 Control part (CPU) 22 Storage part (EEPROM) 23 Receiving part 24 Judging part 25 Transmitting part 26 Switching means (gate circuit, multiplexer) 26a, 26b, 26c Switch

Claims (2)

[Claims] 1. A master unit and a plurality of slave units sequentially cascaded to the master unit via a communication line. Each of the slave units receives data from a higher-level unit cascaded by itself. A communication control unit that determines whether or not the data is addressed to a station, and generates transmission data based on the received data; an operation of which is controlled by the communication control unit; If the transmission data is transmitted to the upper unit, if the received data is not data addressed to the own station, the transmission data is transmitted to the lower unit, and the data transmitted from the lower unit And a switching means for transmitting to the upper unit as it is. 2. Each of the slave units includes a control terminal pulled up via a resistor, a ground terminal connected to the control terminal of a cascaded higher-order unit, and a built-in communication control unit. And means for determining whether or not the own station is the lowest-order slave unit connected in cascade based on the potential of the control terminal and controlling the operation of the switching means.
A communication system according to claim 1.