Patent Application
20070268835
In the conventional redundancy communication control system described above, when data is received simultaneously via the main control channel 2 and the sub control channel 3, it is necessary to determine whether both receive data is identical or not. In addition, it is also necessary to distinguish data received via which channel is valid data. For example, when data is received via both of the main control channel and the sub control channel and both data are compared by the comparator circuit 43 bringing the result that both data are different from each other, a circuit structure for determining which receive data is valid becomes complex in order to distinguish identification information embedded in header information of receive data, to obtain information relating send data from a sender and the like, and there is a problem that miniaturization, weight saving and the like of the device are difficult.
In addition, in order to simplify the circuit structure of the receiver, a hot standby system is employed for receiving data not via the main control channel 2 and the sub control channel 3 simultaneously but only via the main control channel 2 and switching to the sub control channel 3 once a failure occurs in the main control channel 2. In this case, there still is a problem that data cannot be received once a failure occurs in the main control channel 2 when a failure has already occurred in the sub control channel 3 and redundancy becomes meaningless.
The present invention has been made in view of the circumstances, and it is an object thereof to provide a redundancy communication control system and a redundancy communication control method which enable communication without any stop in data transmission and receipt even with a simple circuit structure. The following description will explain the present invention in detail with reference to the drawings illustrating an embodiment thereof.
The control unit 21 at least comprises a processor such as an LSI and transmits a command signal to the controlled unit 24 via the main control channel 22 or the sub control channel 23, or via the main control channel 22 and the sub control channel 23.
By transmitting a command signal via the main control channel 22 and/or the sub control channel 23, the control unit 21 makes the command transmission redundant. Command transmission is classified broadly into two types. One is a dual type to send a command simultaneously to both of the main control channel 22 and the sub control channel 23, and the other is a hot standby type to send a command only to the main control channel 22 and send a command to the sub control channel 23 only when a failure occurs in the main control channel 22.
The controlled unit 24 at least comprises: signal level judging circuits 241 and 241 for examining the signal level of received data; an AND circuit or OR circuit 242 for computing conjunction or disjunction of received data; a data check circuit 243; a receive buffer 244; and an actuator 245 for causing the controlled unit 24 to perform a required operation.
The controlled unit 24 examines the signal level of data received via the main control channel 22 and/or the sub control channel 23 at the signal level judging circuits 241 and 241. When a failure occurs in the main control channel 22 or the sub control channel 23, the signal level of the received data becomes constant at a high state (for example, “1”) or a low state (for example, “0”). Consequently, the controlled unit 24 can determine in which channel a failure has occurred, by examining the signal level.
When the controlled unit 24 determines that the signal level does not maintain “1” for a certain period of time (step S302: NO), the controlled unit 24 determines whether the signal level of the received data maintains a low state, e.g. “0”, for a certain period of time or not (step S303). When the controlled unit 24 determines that the signal level maintains “0” for a certain period of time (step S303: YES), the controlled unit 24 computes disjunction of data received via both channels, with an OR circuit 242 (step S305). That is, the controlled unit 24 computes disjunction of data the signal of which maintains “0” for a certain period of time and data received via a normal channel so as to obtain normal receive data.
It should be noted that the AND circuit or OR circuit 242 is not essential, and only data received via a channel which is determined to be normal may be sent to the data check circuit 243 after distinguishing which channel is normal.
Therefore, the controlled unit 24 determines whether the signal level of data received via the main control channel 22 and/or the sub control channel 23 maintains a high state or a low state continuously for a certain period of time or not at the signal level judging circuits 241 and 241. In particular, determined after reception of a receive data row 41 ends is whether a period of time for which the signal level maintains a certain value, e.g. “1” or “0”, has reached a period of time t1 which is longer than a reception time interval Δt of a case where a receive data row is received normally or not, and it is determined that some failure has occurred in the channel when said period of time has reached the period of time t1.
The controlled unit 24 determines whether a failure has occurred in the main control channel 22 or not (step S306). When the controlled unit 24 determines that a failure has occurred in the main control channel 22 (step S306: YES), the controlled unit 24 transmits information indicating that a failure has occurred in the main control channel 22 to the control unit 21 (step S307). When the controlled unit 24 determines that a failure has occurred in the sub control channel 23 (step S306: NO), the controlled unit 24 transmits information indicating that a failure has occurred in the sub control channel 23 to the control unit 21 (step S308). In which channel a failure has occurred is transmitted to the control unit 21 by, for example, transmitting a channel ID or the like for distinguishing a channel.
Receiving information indicating that a failure has occurred in the main control channel 22, the control unit 21 switches a data transmission channel to the sub control channel 23. Receiving information indicating that a failure has occurred in the sub control channel 23, the control unit 21 announces that a failure has occurred in the sub control channel 23 by display output to the outside or the like. In this manner, the sub control channel 23 can be repaired immediately and it becomes possible to prevent such a situation that data transmission and reception stop due to occurrence of a failure in the main control channel 22.
When the controlled unit 24 determines that the signal level does not maintain “0” for a certain period of time (step S303: NO), the controlled unit 24 determines that both channels function normally and executes a parity check or the like with the data check circuit 243 for received data, or receive data received via the AND circuit or OR circuit 242, so as to verify the consistency of the receive data (step S309). The controlled unit 24 temporarily stores data after the termination of data check in the receive buffer 244, reads out necessary data from the receive buffer 244 according to each actuator 245 and transmits the data to the corresponding actuator 245 (step S310). Each actuator 245 applies command analysis to received data and makes an operation according to designation to be performed.
It is preferable to avoid mistakenly determining that a channel failure has occurred while communication is not performed. Therefore, the control unit 21 transmits dummy data which makes it possible to detect variation of the signal level at a certain time interval t2.
While communication is not performed as shown in
Therefore, while communication is not performed, the control unit 21 transmits dummy data 51, 51, . . . having a signal level of “1” at a time interval t2 (t1>t2). The controlled unit 24 never fails to detect dummy data 51 even when communication is not performed and can avoid mistaken determination. It should be noted that the timing for starting transmission of dummy data 51, 51, . . . is not limited especially, and transmission may be started at the timing when the connection of communication is opened, and stopped at the timing when connection is established, for example.
With the present embodiment, as described above, since the signal level of received data always varies while data communication is performed, it is possible to determine that abnormality has occurred in communication using the channel when it is detected that the signal level is fixed at a high state or a low state for a certain period of time. Consequently, the normal/abnormal of a channel can be determined precisely in a simple circuit structure without the need to provide a comparator circuit of receive data, a circuit for determining whether received data is valid data or not and the like, and it becomes possible to realize redundancy communication without any stop in data communication. In addition, by transmitting dummy data having a signal level which is not fixed at a high state or a low state for a certain period of time, for example, it becomes possible to avoid false recognition of a state in which no data is transmitted or received as a failure in a channel.
It should be noted that a plurality of controlled units 24, 24, . . . may be connected for one control unit 21 although the embodiment described above explains a case where one controlled unit 24 is connected for one control unit 21. It should be understood that the cost-down effect is enhanced by simplifying the circuit structure of the controlled units 24, 24, . . . .
In addition, the main control channel 22 and the sub control channel 23 are not limited to correspond to the serial transmission system, and the same effect can be expected in a case where the channels correspond to the parallel transmission system, for example.
As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-140484 | May 2006 | JP | national |
