JPH05219075A - Communication system - Google Patents

Abstract

PURPOSE:To obtain a communication equipment which can obtain immediately the right of data transmission even in the case the number of installations of the communication equipment is large and in the case the traffic quantity on a shared bus is large, in the communication equipment for transmitting and receiving data through the shared bus. CONSTITUTION:The system is provided with plural communication equipments for transmitting and receiving data through a shared bus, and each communication equipment thereof is provided with a transmission right obtaining part 20 for sending out a transmission request signal and obtaining the right of transmission, a transmission request detecting part 10 for executing polling in order from the communication equipment which follows itself and detecting the communication equipment which sends out a transmission request, and a control part 15 for obtaining the right of transmission by actuating the transmission right obtaining part 20 at the time when the transmission request is generated, and also, actuating the transmission request detecting part 10 after data transmission, and transferring the right of transmission to the communication equipment which sends out the transmission request.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system,
Particularly, it relates to a communication system including a plurality of communication devices connected by a shared bus.

[0002]

2. Description of the Related Art A conventional communication device is composed of one master device and a plurality of slave devices connected via a shared bus, and the master device has a fixed right to control the shared bus. When the transmission request signal from the slave device is received, the polling operation is started from a fixed device address.

The operation of the conventional communication device when a transmission request signal is generated will be described with reference to the flowchart of FIG.

.. The master device checks whether or not there is a transmission request signal on the shared bus (S31 in FIG. 3).

.. Upon receiving the transmission request signal, the master device sets the device address to the minimum value registered in advance (S32 in FIG. 3).

[0006] The master device polls the slave device set in the device address (S in FIG. 3).
33).

[0007]. If the slave device polled is not the source of the transmission request signal (S34 in FIG. 3), the master device advances the value set in the device address (S35 in FIG. 3).

[0008] By repeating the above, if the slave device that has performed the polling operation is the source of the transmission request signal, the master device issues a data transmission instruction to the slave device (S36 in FIG. 3).

[0009]

However, in the above-mentioned conventional example, since the polling operation is always started from a fixed device address, the number of slave devices installed increases and the traffic volume on the shared bus increases. As the number of devices increases, there is an inconvenience that the opportunity to acquire the data transmission right is significantly restricted depending on the device address.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the conventional example, and particularly in a communication device that transmits and receives data via a shared bus, when the number of installed communication devices is large or traffic on the shared bus is large. An object of the present invention is to provide a communication system in which a data transmission right can be immediately acquired even when the amount is large.

[0011]

In view of the above, according to the present invention, one communication device sends a transmission request signal to acquire a transmission right, and a communication right acquisition unit sequentially polls and transmits from a communication device following the transmission right acquisition unit. A transmission request detection unit that detects the communication device that sent the request and a transmission right acquisition unit that activates the transmission right acquisition unit when the transmission request occurs, and activates the transmission request detection unit after data transmission and sends the transmission request. And a control unit that transfers the transmission right to the communication device. This aims to achieve the above-mentioned object.

[0012]

The control unit of the communication device that has issued the transmission request activates the transmission right acquisition unit. The transmission right acquisition unit sends a transmission request signal to the shared bus. On the other hand, the control unit of the communication device having the transmission right activates the transmission request detection unit when the data transmission is completed. Upon receiving the transmission request signal, the transmission request detection unit of the communication device having the transmission right polls the communication devices following it in order. Upon receiving the polling signal, the transmission right acquisition unit of the communication device that has transmitted the transmission request signal notifies the communication device having the transmission right that it has transmitted the transmission request signal. When the transmission request detection unit of the communication device having the transmission right detects the communication device that has transmitted the transmission request signal, it notifies the control unit. The control unit of the communication device having the transmission right notifies the communication device that has transmitted the transmission request signal of the transfer of the transmission right. The communication device which has transmitted the transmission request signal transmits the data when the transmission right is transferred.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

The embodiment shown in FIG. 1 is a communication device for transmitting and receiving data via a shared bus, and a transmission right acquisition unit 20 for transmitting a transmission request signal to the shared bus to acquire a transmission right, and a communication device following itself. A transmission request detection unit 10 that detects the communication device that has sent a transmission request by polling in order from
A control unit 15 that activates the transmission right acquisition unit 20 to acquire the transmission right when a transmission request occurs, and activates the transmission request detection unit 10 after data transmission to transfer the transmission right to the communication device that has transmitted the transmission request; It is equipped with.

Here, the transmission request detection unit 10 has a device address register 1 that stores the device address of the communication device.
2, a transmission request signal determining unit 11 which is activated by the control unit 15 and checks whether there is a transmission request signal on the shared bus, and stores the device address in the device address register 12 if there is a transmission request signal; A polling unit 13 that is activated by the determination unit 11 and performs a polling operation on a communication device having a device address stored in the device address register 12, and checks whether the polled communication device is the transmission source of the transmission request signal and transmits the signal. If the source is not the source, the contents of the device address register 12 are advanced, and the source determining unit 14 notifies the control unit 15 when the source of the transmission request signal is detected.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. Here, it is assumed that a plurality of communication devices having different device addresses are connected via one shared bus.

(1) Operation of communication device having transmission right:

.. The control unit 15 activates the transmission request signal determination unit 11 when the data transmission is completed.

.. The transmission request signal determination unit 11 checks whether or not there is a transmission request signal on the common bus (S21 in FIG. 2).

[0020]. Upon receiving the transmission request signal, the transmission request signal determination unit 11 stores its own device address in the device address register 12 (S22 in FIG. 2).

[0021]. Further, the transmission request signal determination unit 11 advances the content of the device address register 12 by one (S in FIG. 2).
23). However, it is checked whether or not this device address exceeds the maximum value of the device address registered in advance (S24 in FIG. 2), and if it exceeds the maximum value, the device registered in the device address register 12 in advance. The minimum value of the address is stored (S25 in FIG. 2).

.. When the device address is stored, the transmission request signal determination unit 11 activates the polling unit 13.

.. The polling unit 13 reads the device address from the device address register 12 and performs a polling operation on the communication device (S26 in FIG. 2). Then, the polling unit 13 notifies the transmission source determination unit 14 that the polling operation has been performed.

[0024]. The transmission source determination unit 14 analyzes the signal from the polled communication device and determines whether it is the transmission source of the transmission request signal (S27 in FIG. 2).

[0025]. The origin determination unit 14 analyzes the result,
If it is determined that the communication device that has polled is not the source of the transmission request signal, the content of the device address register 12 is incremented by one (S23 in FIG. 2), and the polling unit 13 is requested to poll. However, it is checked whether or not this device address exceeds the maximum value of the device address registered in advance (S24 in FIG. 2), and if it exceeds the maximum value, the device registered in the device address register 12 in advance. The minimum value of the address is stored (S in FIG. 2).
25). The transmission source determination unit 14 repeats the operation until it is determined that the polled communication device is the transmission source of the transmission request signal.

As a result of the analysis, when the transmission source determining unit 14 determines that the polled communication device is the transmission source of the transmission request signal, it notifies the control unit 15 of the device address of the transmission request signal transmission source. ..

[0027]. Upon receiving the device address of the transmission source of the transmission request signal from the transmission source determination unit 14, the control unit 15 notifies the communication device of the transfer of the transmission right (S28 in FIG. 2).

(2) Operation of the communication device in which the transmission request is generated:

.. When a transmission request is generated, the control unit 15 activates the transmission right acquisition unit 20.

.. The transmission right acquisition unit 20 sends a transmission request signal on the common bus.

.. When polling is received from the communication device having the transmission right, the transmission right acquisition unit 20 notifies the communication device having the transmission right that it is the one that has transmitted the transmission request signal.

.. When the transfer of the transmission right is notified from the communication device having the transmission right, the control unit 15 sends the data specifying the device address of the data transfer destination to the shared bus.

.. The above operation (1) is performed.

[0034]

Since the present invention is constructed and functions as described above, according to the present invention, the device address at the start of the polling operation can be made variable, which enables the communication device connected to the shared bus. It is possible to provide an unprecedented excellent communication system in which the data transmission right can be immediately acquired even when the number of installations is large or the traffic volume on the shared bus is large.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the communication device having the transmission right of FIG.

FIG. 3 is a flowchart for explaining the operation of the communication device having a transmission request in FIG.

[Explanation of symbols]

 10: Transmission request detection unit 15: Control unit 20: Transmission right acquisition unit

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 8020-5K H04L 13/00 305 D

Claims (2)

[Claims] 1. In a communication system including a plurality of communication devices for transmitting and receiving data via a shared bus, each communication device sends a transmission request signal and acquires a transmission right, and And a transmission request detection unit that detects a communication device that has sent a transmission request by sequentially polling from the communication device and a transmission right acquisition unit that activates the transmission right acquisition unit when the transmission request occurs to acquire the transmission right and transmit the data. And a control unit which later activates the transmission request detection unit and transfers the transmission right to the communication device which has transmitted the transmission request. 2. The transmission right transfer unit includes a device address register that stores a device address, and a transmission request signal determination unit that stores the device address in the device address register when there is a transmission request signal on the shared bus. A polling unit that is activated by the transmission request signal determination unit and performs a polling operation on a communication device having a device address stored in the device address register; and a communication device polled by the polling unit 2. The communication system according to claim 1, further comprising: a sender determination unit that advances the contents of the device address register if the sender is not the sender and notifies the control unit if the sender of the transmission request signal. ..