JPH04219038A - Bus switching device - Google Patents

Abstract

PURPOSE:To suppress an external disturbance on a system connecting to a bus by disconnecting the bus immediately when dissidence of a connection direction of the bus takes place because of a defect of a component or the like of a repeater. CONSTITUTION:First and 2nd repeaters 1, 2 are respectively provided with changeover execution sections 11, 21 selecting respectively the connection state between any of 1st and 2nd buses B1a, B1b and a 3rd bus BS1 and the connection state between any of 4th and 5th buses B2a, B2b and a 6th bus BS2 and with changeover control sections 12, 22 outputting a switching signal, and further initializing means 13, 23 and error signal generating means 14, 24 generating an error signal outputted to an opposite changeover control section when a switching signal outputted from its own changeover control section and a switching signal outputted from opposite changeover control section are dissident for a prescribed time or over. When a fault takes place, the bus is disconnected.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a bus switching device applied to, for example, a system with duplexed buses in order to improve reliability, and more specifically, to synchronize signals from two computer systems with each other. The present invention relates to a bus switching device that is free from failures due to failures in switching operations in repeaters or indicators that issue switching instructions in a system that outputs to a duplex bus via a repeater that performs switching operations.

0002

2. Description of the Related Art FIG. 4 is a conceptual diagram of a conventional bus switching device of this type. In the figure, BS1 and BS2 are buses with a redundant configuration, to which, for example, a control station in charge of process control is connected. 1 and 2 are repeaters that perform switching operations in synchronization with each other; 3 is an indicator that outputs an instruction signal that instructs switching operations in these repeaters; 51 and 52 are computer systems;
, 2 so that the buses B1a and B2a output from one computer system 51 are connected to buses BS1 and BS2, respectively, or the other computer system 5
Buses B1b and B2b departing from 2 are buses BS1,B
The buses are switched so that they are respectively connected to S2.

3 is a switching indicator 3, which connects two repeaters 1,
2 is monitored by signals SIG1 and SIG4, and if any abnormality occurs, the indicator 3 sends control signals SIG2 and SIG3 to each repeater 1 and 2 to instruct them to stop the relay operation. It is configured as follows.

0004

[Problems to be Solved by the Invention] In the conventional device having such a configuration, when the repeater or switching indicator 3 fails, or when this indicator is removed from the system, the two computer systems 51, There is a problem in that it is not possible to quickly respond to abnormal situations such as signals from 52 being output to each bus separately, or not being output to one bus, or switching not being synchronized.

[0005] The present invention has been made in view of these points, and its purpose is to reliably detect an abnormality in a repeater and disconnect the bus when an abnormal situation such as a mismatch in the connection direction of the bus occurs. To provide a bus switching device capable of minimizing disturbance to a system connected to the bus and maintaining high reliability of the system.

[0006]

[Means for Solving the Problems] The present invention for achieving such objects includes a first repeater that connects either a first bus or a second bus to a third bus. , a fourth bus and a second repeater that connects either one of the fifth buses to the sixth bus, and the bus switching between the first repeater and the second repeater is performed externally. A bus switching device that performs switching based on a switching instruction signal from a bus, wherein each of the first and second repeaters is provided with a connection state between one of the first and second buses and a third bus, and a fourth bus. , a switching execution section that switches the connection state between the fifth bus and the sixth bus, and a switching control section that outputs a switching signal instructing the connection state of the switching execution section.

[0007] The initializing means inputs the switching signal outputted from its own switching control section and the switching signal (S1, S2) outputted from the switching control section of the other party, respectively, and determines whether the two switching signals do not match for a certain period of time or more. If there is,
and error signal generation means for activating an error signal output to the other party switching control section.

[0008]

[Operation] Each element within each repeater has the following operation. The initializing means performs an initializing operation when the power is turned on, and outputs an initializing signal to the switching control section of the partner repeater.

The switching control section inputs the switching signal from the partner repeater, the error signal from the error signal generation means, and the initialization signal from the initialization means, and depending on the state of these signals, Controls the switching signal output to the switching execution unit.

0010

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a first repeater that selects either one bus B1a coming out from one computer system (not shown) or one bus B1b coming out from the other computer system, This is for relaying to bus BS1. 2 is a second repeater, which is connected to another bus B2a from the other computer system (not shown).
and one other bus B2b coming out from the other computer system, and relay the selected bus to bus BS2. A switching command signal is given to each of the first and second repeaters 1 and 2 from a switching indicator 3, and each repeater 1 and 2 is given a switching command signal from a switching indicator 3.
, 2 perform bus switching to connect the buses BS1 and BS2 to one computer system or the other computer system.

[0011] In each of the first and second repeaters, 11, 2
1 is a switching execution unit, and 12 and 22 are switching control units, and based on switching signals S1 and S2 outputted from the switching execution units 11 and 21, for example, two buses B1a, B2a to bus BS1, BS
2, the connection is switched and the transmission signal is relayed. In addition,
41, 42, 43, 51, 52, and 53 are transceivers inserted into each bus line.

Initialization means 13 and 23 generate initialization when the power is turned on, and send out initialization signals INZ1 and INZ2, respectively, to the switching control section in the partner repeater. Reference numerals 14 and 24 denote error signal generation means, which input the switching signal outputted from the switching control section of its own repeater and the switching signals S1 and S2 outputted from the switching control section of the opposite repeater, respectively, and generate two switching signals. If the signals S1 and S2 do not match for a certain period of time or more, it is configured to activate error signals ERR1 and ERR2 that are output to the other party switching control section.

[0013] The switching control units 12 and 23 are constituted by a state machine using, for example, a programmable logic array together with an error signal generating means, and are configured to output a switching signal from the opposite repeater and an error signal from the error signal generating means. , and an initialization signal from the initialization means, respectively, and the states of switching signals S1 and S2 to the switching execution section are controlled according to the states of these signals. Furthermore, if a switching indicator 3 is present, an instruction signal from there is input.

FIG. 2 is a state transition diagram showing the operation when the switching control section 12 (22) and the error signal generating means 14 (24) are configured as a state machine. In the switching control unit 12, the switching control signal S1 outputted by itself
and the switching control signal S2 from the other party's repeater are equal (S1=S2), and the error signal E from the other party's
When RR2 is inactive, it is in the state of ST1. In such a state ST1, if the switching control signal S1 outputted by itself is no longer equal to the switching control signal S2 from the other party's repeater (S1≠S2), or if an error signal from the other party's When ERR2 becomes active, the state transitions to ST2.

In this state of ST2, the switching control signal S1
and switching control signal S2 are equal (S1=S2)?
, initialization signal INZ from the own side or the other side
becomes active, the state returns to ST1. In addition, in this state of ST1, the switching control signal S
1 and the switching control signal S2 are not equal (S1≠S2)
, or if the error signal ERR2 from the other party is active, the state transitions to ST3. In addition, in this state of ST3, the switching control signal S
1 and the switching control signal S2 are not equal (S1≠S2)
, or if the error signal ERR2 from the other party is active, the state transitions to ST4. In the state of ST3, if the switching control signal S1 and the switching control signal S2 become equal (S1=S2) or the initialization signal INZ from the local side or the other party becomes active, the process returns to the state of ST1.

When the state transitions to ST4, it acts on the error signal generating means and outputs the error signal E.
RR is activated and the content of the switching control signal S1 is set to instruct bus disconnection.

The operation of the apparatus configured as described above will be explained next. FIG. 3 is a time chart showing operations during normal operation and when an error occurs. In this example, in the initial operating state, the first and second repeaters 1 and 2 connect two buses B1a and B2a coming out of one computer system (system a side) to buses BS1 and BS2. Assume that the computer system is connected to each computer system, and then connected to the other computer system (system b side). Figure 3(a)
is the normal operation, and when the switching indicator 3 instructs to connect the two buses B1b and B2b coming out from the other system b side to the buses BS1 and BS2, respectively, from the initial state, In the first and second repeaters, the switching control units 12 and 22 receive this instruction signal and, for example,
Switching execution units 11 and 21 within an allowable time of 8 μS.
performs bus switching so that it is connected to the b-side system. If the bus switch takes place within the allowed time,
The error signals from each repeater are all inactive.

FIG. 3(b) shows the operation at the time of abnormality,
Here, a case is shown in which the second repeater 2 does not perform bus switching within the allowable time. In this case, in the first repeater 1, the error signal generation means 14 detects that the states of the input switching control signals S1 and S2 do not match, and that the mismatch period is longer than a predetermined time (for example, the permissible time of 48 μS or more). If the process continues (time), it transitions to state ST4 in FIG. 2, and the error signals ERR1 and EER2 become active as shown. Switching control section 1
2 and 22, upon receiving this error signal, output a command signal to the switching execution units 11 and 21 to disconnect (release the connection) the bus.

[0019] Due to such an operation, if a problem occurs in the operation of the repeater, such as bus switching not being performed synchronously within the allowable time, the redundant configuration buses connected to each system can be quickly connected. Separated. therefore,
Disturbances to the systems connected to the bus can be minimized. The above operation is reliably performed even when the switching indicator 3 is removed from the system. In addition,
Each of the first and second repeaters receives an initialization signal INZ from the other repeater, and if this initialization signal is active, the other repeater does not exist or is not functioning. It is determined that a mismatch in the bus switching control signals cannot occur, and the error signal is not activated. That is, the second
In the figure, the state is returned from ST2 or ST3 to ST1, and the state does not transition to ST4.

[0020]

[Effects of the Invention] As explained above in detail, according to the present invention, when a mismatch in the connection direction of the bus occurs due to a defect in the parts constituting the repeater, etc., it is possible to immediately disconnect the bus. This minimizes disturbances to the system connected to the bus and provides highly reliable equipment. Such an effect functions effectively even when the switching indicator is removed.

[Brief explanation of the drawing]

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

FIG. 2 is an operation transition diagram showing the operation when the switching control section and the error signal generation means are configured by a state machine.

FIG. 3 is a time chart showing operations during normal operation and when an error occurs.

FIG. 4 is a conceptual diagram of the configuration of a conventional bus switching device.

[Explanation of symbols]

1 First repeater 2 Second repeater 11, 21 Switching execution section 12, 22 Switching control section 13, 23 Initializing means 14, 24 Error signal generating means 3 Switching indicator 41, 42, 43, 51, 52, 53 Transceiver BS1, BS2 bus

Claims (1)

[Claims] Claim 1: A first bus (B1a) and a second bus (B1a).
1b) to the third bus (BS1), and connects either the fourth bus (B2a) or the fifth bus (B2b) to the sixth bus (BS1). a second repeater connected to a BS2), the bus switching device performs bus switching between the first repeater and the second repeater based on a switching instruction signal from the outside; The connection status between either the first or second bus and the third bus, or the connection status between the fourth or fifth bus and the sixth bus is sent to each of the first and second repeaters. A switching execution section that performs switching, a switching control section that outputs a switching signal instructing the connection state in this switching execution section, an initializing means, and a switching signal output from its own switching control section and a switching control section of the other side. and an error signal generating means for inputting the output switching signals (S1, S2) and activating an error signal to be output to the switching control unit on the other side if the two switching signals do not match for a certain period of time or more, The switching control section inputs a switching signal from the other party's repeater, an error signal from the error signal generating means, and an initialization signal from the initialization means, and controls its own switching according to the states of these signals. A bus switching device characterized by controlling a switching signal output to an execution unit.