JPH04268847A - Bus communication system - Google Patents

Abstract

PURPOSE:To recognize the occurrence of the accident of a machine, and to prevent a whole system from being influenced by this by outputting a forced answer request signal at every prescribed period at a state detecting side. CONSTITUTION:The machines 2 to 5 connected to a bus B are provided with a control means consisting of a microcomputer 1, and are provided with a state detecting means which outputs an answer request signal to another machine, and simultaneously, receives its answer, and discriminates the state. Namely, the state detecting means outputs the answer request signal to the specified machine, and if an answer signal is not received even after the lapse of prescribed time, it outputs the signal to request a forced answer. Accordingly, an answering side can output the answer signal as soon as it is prepared, and the repsonsiveness of the system can be improved, and simultaneously, the occurrence of the accident can be recognized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus communication system applied to, for example, a home bus system.

0002

[Prior Art] In a home bus system, etc., each device is generally connected by a bidirectional communication bus, and operation instruction information, detection information, status determination information, etc. are exchanged between each device. Appropriate operation control can be achieved depending on the state of the device.

For example, in a system in which devices such as a control device, a VTR, an AV selector, and a monitor device are connected via a bus, the control device issues a response request signal to the VTR to inquire whether a recording tape is loaded. When the VTR issues a response signal indicating loading a recording tape, the control device
It is possible to confirm the loading state of the recording tape in the system, and based on this confirmation operation, a system operation is possible in which the control device supplies a recording command to the VTR.

[0004] By the way, the following two communication methods are considered when a certain device A checks the status of another device B in the system. First, as shown in FIG. 6, when device A first outputs a response request signal a1 to device B, device B responds by executing an answer detection process b1 to detect the answer to the inquiry. , is a method in which response signal output processing b2 is executed on device A at an arbitrary timing after an answer is detected.

Second, as shown in FIG.
When a response request signal a1 is output to the device B, the device B executes an answer detection process b1 to detect the answer to the inquiry, but after detecting the answer, it waits for the output of a trigger signal from the device A for requesting an answer. Then, device B executes response signal output processing b2 to device A at the timing of trigger signal output a2.

[0006]

[Problems to be Solved by the Invention] The above first communication method makes use of the response speed of device B, and has the advantage of promoting improved system responsiveness; however, on the other hand, if device B If the power is suddenly turned off or if a response to a response request signal cannot be obtained due to a runaway in the software, device A will continue to wait for a response signal from device B. There is a big problem that the abnormality of device B will be propagated, that is, even if an abnormality occurs only in device B, the entire system will not be able to operate normally.

[0007] Furthermore, in the second communication method, since device A manages the response signal output timing of device B,
If no response signal is obtained at the time of the trigger, it can be recognized that an abnormality has occurred in device B, and predetermined abnormality processing can be performed.
In other words, a considerable amount of time must be allowed from the output of the response request signal to the output of the answer request trigger signal. In particular, if device B has to make further inquiries to other devices C, D, etc. in order to detect the answer, the answer search time will accumulate and become long, so take this into consideration. The problem is that only a system with very poor responsiveness can be realized.

[0008]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to output a response request signal to other devices in a system connected by a bidirectional communication bus, one or more devices having a state detection means capable of determining the state of other devices by obtaining a response signal from the device, and a response signal in response to a response request signal inputted via a two-way communication bus. In a bus communication system consisting of one or more devices having response means capable of outputting a response, the state detection means of the one or more devices includes a first response request signal that outputs a first response request signal requesting a response. a signal generating means; a timer means that starts counting based on transmission of the first response request signal or detection of the standby request signal; and a timer means that forcibly requests a response when the elapse of a predetermined period is detected by the timer means. a second signal generating means for outputting a second response request signal; a response detecting means for detecting a response signal to the first or second response request signal; The state detection operation control means terminates the state detection operation if the standby request signal is not obtained, and the response means included in the one or more devices responds to the input first or second response request signal. The system is configured to include a response signal generation means for outputting a response signal in response to the second response request signal, and a standby request signal generation means for outputting a standby request signal when the response signal cannot be outputted in response to the second response request signal. .

[0009]

[Operation] After device A, which inquires about the status of device B, outputs the first response request signal, device B outputs a response signal when an answer is ready, thereby increasing the responsiveness of device B. will be effectively reflected in the responsiveness of the entire system. Further, if device B does not output a response signal or a standby request signal after a predetermined period of time has elapsed and the second response request signal is output, device A can recognize that an abnormality has occurred in device B.

0010

[Embodiment] Fig. 1 shows an example of a home bus system to which the bus communication system of the present invention is applied, and 1 is a control device that can issue operation commands to each device in the system and control predetermined operations. , 2 and 3 are VTR, 4 is AV
Selector 5 is a monitor device, and output terminals 2a and 3a for audio and video signals of VTRs 2 and 3 are A.
It is connected to the input terminal 4a of the V selector and selectively supplied to the output terminal 4b. The output terminal 4b of the AV selector 4 is connected to the input terminal of the monitor device 5. Information and commands are exchanged between these devices via a bidirectional communication bus B.

For example, in such a home bus system, all or part of each device connected by bus B has a control means constituted by a microcomputer, and controls the operation of each device and gives instructions to other devices. In addition to controlling communication such as information supply and information supply, it is also necessary to detect the current state of the relevant device when issuing operation commands to other devices. A state detection means is formed by software, which outputs a response request signal having predetermined inquiry contents and receives the answer to determine the state. Similarly, response means for detecting an answer matching the inquiry content in response to a response request signal issued from the state detection means of another device and outputting it as a response signal is also formed by software.

The bus communication system of the present invention is particularly realized by the state detection means and response means formed as part of the control means of each device, and the state detection means and response means are implemented by software functions. It is configured as a block as shown in FIGS. 2 and 3.

That is, as shown in FIG. 2, the state detection means 20 includes a state detection operation control means 21 that executes a requested state detection operation in response to a command for determining the state of another specific device from the central control unit 10, and a timer device. Alternatively, a timer management means 22 that includes a soft counter and manages time during the state detection operation, a response request signal generation means 23 that generates and outputs a corresponding response request signal, and a timer management means 22 that is equipped with a soft counter and performs time management during the state detection operation; Forced response request signal generation means 2 for generating and outputting a forced response request signal requesting a forced response from the corresponding device when the response signal is not received.
4, and a response signal detection means 25 for receiving and detecting a signal such as a supplied response signal.

On the other hand, the response means 30 detects that a response request signal has been transmitted from the state detection means 20 of another device and determines the content of the inquiry. forced response request signal detection means 32 for detecting that the forced response request signal has been transmitted;
An answer search means 33 that performs a search operation regarding the contents of the inquiry based on the response request signal, and a response signal generation means that generates a response signal when an answer is obtained and outputs it to the state detection means 20 of the device that has transmitted the response request signal. 34, and standby request signal generation means 35 which generates a standby request signal and outputs it to the state detection means 20 of the device on the response request signal sending side when no answer is obtained at the time when the forced response request signal is transmitted. It consists of

Each device in FIG. 1 has the state detection means 20 and the response means 30, respectively. For example, when the control device 1 wants to cause the VTR 2 to perform a recording operation, the control device 1 needs to detect whether a tape cassette is loaded in the VTR 2 and a recording tape is being loaded. , the state detection means 20 of the control device 1 is VT
A response request signal is issued to the response means 30 of R2 to inquire about the loading status of the tape cassette, while VTR2
In response, the response means 30 detects the tape cassette loading and outputs the answer to the inquiry as a response signal to the state detection means 20 of the control device 1. The operations of the state detection means 20 and response means 30 executed during such system operation in this embodiment are shown in the flowcharts of FIGS. 4 and 5. Each step of the flowchart is F101 to F110 and F201 to F20.
Indicated by 6.

First, when a case occurs in which the central control unit 10 of a certain device wants to inquire about another device in order to perform some kind of operation control, the state detection means 20 uses the state detection operation control means 21 to perform the state detection operation. is started (F101). First, a response request signal including the inquiry content is outputted from the response request signal generating means 23 to the corresponding device via bus B (F102
), at the same time, the timer device in the timer management means 22 is reset and counting starts (F103). Then, it enters a standby state for a response signal from the output destination response means 30. Note that the control means as a whole can be used for other processing during this standby time.

During the standby period, the timer management means 22 executes a time counting operation, and if a response signal is transmitted as an answer to the response request signal output within a predetermined time and detected by the response signal receiving means 25, the state is changed. The detection operation control means 21 supplies the content of the response to the central control unit 10 to hold it (F105), and ends the state detection operation. The content of the response is processed by the central control unit as decision data for equipment control that is subsequently executed.

However, if no response signal is obtained even after waiting for a predetermined period of time, the forced response request signal generating means outputs a forced response request signal, which is a trigger signal for forcibly requesting a response (F107). If a response signal is detected in response to this, the content of the response signal is transmitted to the central control unit 10.
and completes the status detection operation (F108→F105
), or if a signal indicating ``investigating'' is sent from the response means 30 of the inquiry destination, the timer is reset again, assuming that a standby request has been made because it takes time to search for an answer. Enters response signal standby state (F109→F103). When the response signal is detected, its contents are supplied to the central control unit 10 and the state detection operation is completed.

However, even if a forced response request signal is sent, if neither a response signal nor a standby request signal indicating ``under investigation'' is supplied, an accident such as a power failure or runaway in the software program may occur in the device being inquired about. Recognizing that an error has occurred, the state detection operation control means 21 notifies the central control unit 10 of the error occurrence, and ends the state detection operation (F110).
).

On the other hand, when a response request signal is detected by the response request signal detecting means 31 (F201) in the response means 30 in the device to which the status inquiry is made, the answer search means 33
performs an operation to search for an answer corresponding to the inquiry content of this response request signal (F202). When the answer is retrieved by the search operation (F205), the response signal generating means 34 outputs a response signal indicating the content of the answer to the state detecting means 20 of the inquiry source (F206). However, if a forced response request signal is supplied from the status detection means 20 on the inquiry side during the search operation, since an answer cannot be answered yet, the standby request signal generation means 35 outputs a standby request signal with the content "under investigation" ( F203→F204)
. Then, when the search operation is completed, a response signal is output (F206).

In the bus communication system of this embodiment, the status detection means 20 and response means 30 in each device in the home bus system perform the above operations, thereby creating a system that has good responsiveness and can cope with the occurrence of errors. It will become a reality. In other words, during the waiting time in the status detection means 20 on the inquiry side, the response means 30 on the inquiry destination
Since the response signal can be output at any timing, that is, at the end of the answer search operation, there is no need to wait for the output of the response signal, and the responsiveness of communication increases according to the responsiveness of the device at the destination of the inquiry. be able to.

[0022]Furthermore, the condition detection means 20 outputs a forced response request signal at regular intervals, and the response by the response signal or standby request signal is confirmed, so that if an error occurs in the device to be queried, Because the response signal or the standby request signal is not obtained, the status detection means 20 on the inquiry side can recognize the occurrence of the error and stop the status detection operation, so the equipment on the inquiry side can detect an error, etc. in the equipment on the inquiry destination. It is also possible to prevent the entire system from being disabled due to the influence of Of course, if it takes time to search for an answer, especially if the device being queried needs to output a response request signal to another device to perform the query operation in order to search for an answer, the answer search time will accumulate. Although this will take a considerable amount of time, the status detection means 20 can confirm from the standby request signal that the time is not being extended due to an error, so there is no problem.

[0023] Even if the state detection means 20 transmits a response request signal to a plurality of other devices at once, the number of timer devices corresponding to the number of devices should be provided, or the number of timer devices should be Even if there is only one device, if the response request signal transmission time is managed for each device, the process of this embodiment can be performed simultaneously for all the devices that are the destination of the inquiry.

Although FIG. 1 shows an example of a home bus system that has a control device 1 that controls the entire system, even in a home bus system that does not have such a control device 1, there is a difference between the control means of each device. It goes without saying that the present invention can be applied as a state detection means and a response means when exchanging information.

[0025]

[Effects of the Invention] As explained above, in the bus communication system of the present invention, the response means can output the response signal at the stage when it is ready, that is, the communication responsiveness of the system depends on the ability of each device. In addition, the state detection means outputs a forced response request signal to the response means at predetermined intervals to request a response signal or a standby request signal, and if these are not detected, Since the equipment on the response means side can recognize that an accident has occurred, the equipment on the status detection means can handle the occurrence of an accident.In other words, even if there is a device in the system that is unable to operate normally, the system as a whole will not be affected. The effect is that it has no effect.

[Brief explanation of the drawing]

FIG. 1 is an example of a home bus system to which an embodiment of the present invention is applied.

FIG. 2 is a functional configuration diagram of a state detection means of this embodiment.

FIG. 3 is a functional configuration diagram of a response means of this embodiment.

FIG. 4 is a flowchart illustrating the operation of the state detection means of this embodiment.

FIG. 5 is a flowchart illustrating the operation of the response means of this embodiment.

FIG. 6 is an explanatory diagram of an example of a conventional bus communication method.

FIG. 7 is an explanatory diagram of an example of a conventional bus communication method.

[Explanation of symbols]

10 Central control section 20 Status detection means 21 Status detection operation control means 22 Timer management means 23 Response request signal generation means 24 Forced response request signal generation means 25 Response signal detection means 30 Response means 31 Response request signal detection means 32 Forced response request signal detection means 33 Answer search means 34 Response signal generation means 35 Standby request signal generation means

Claims (1)

[Claims] [Claim 1] The status of other devices can be determined by outputting a response request signal to other devices in a system connected by a bidirectional communication bus and obtaining a response signal from the other devices. Consisting of one or more devices having a state detection means and one or more devices having a response means capable of outputting the response signal in response to the response request signal input via the two-way communication bus. In the bus communication system, the state detection means includes a first signal generation means for outputting a first response request signal requesting a response, and a state detection means based on the transmission of the first response request signal or the detection of the standby request signal. a timer means for starting counting; a second signal generating means for outputting a second response request signal for forcibly requesting a response when the elapse of a predetermined period is detected by the timer means; response detection means for detecting a response signal to the response request signal; and state detection operation control means for terminating the state detection operation if a response signal or standby request signal is not obtained in response to at least the second response request signal. The response means includes a response signal generation means for outputting a response signal in response to an input first or second response request signal, and a response signal for outputting a response signal in response to the second response request signal. A bus communication system characterized by comprising standby request signal generating means for outputting the standby request signal when the standby request signal is not possible.