JPS60256240A - System switching system - Google Patents

Abstract

PURPOSE:To simplify the system constitution by allowing a controller in a remote device to be operated in following to and in synchronizing with a clock fed from a host device so as to eliminate a synchronizing circuit between controllers of a transmission line and a clock generating source applying a clock to the controller. CONSTITUTION:A duplicated host device is connected to a microcomputer muP51 of the remote device via a data and an address bus, an ROM 152 and an RAM 153 are connected to the data bus and a decoder 154 is connected to the address bus. Moreover, a phase generating circuit 156 is connected to a clock terminal of the muP51 and a clock interruption detection circuit 170 is connected to a reset terminal. Further, the clock from a selection circuit 157 connected to the system 0 or 1 of the host side is fed to circuits 156, 170 and an interface circuit 164. Then the muP51 is activated in following to and in synchronizing with the clock from the host side so as to eliminate the need for the synchronizing circuit and the clock generating source of the remote device thereby simplifying the constitution of system changeover system.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a system switching method, and more specifically, to a selection method (1) for drawing in one side of a duplicated data transmission path. The present invention relates to a system switching system suitable for selecting a transmission path for transmission in synchronization with a clock.

[Background of the invention]

Prior to the detailed description of the present invention, the prior art will be described. 2
A typical example of a method for selecting a multiplexed transmission path is shown in the first example.
As shown in the figure. In Figure 1, l is the host device (HO8T
) and is duplicated. 2 is a remote device (RT
(abbreviated as ), and is single layered. 3 and 4 are transmission lines connecting the HO8T1 and the plurality of RTs2. HO8Tl and R
Data transmission between T2 is a slave synchronization method, and HOS T
] The TR2 transmits and receives data in synchronization with the clock supplied from the TR2. In this case, the TR2 transmits and receives data to and from the TR2 at a predetermined time position, that is, the time division multiplex transmission method is used. In this method, the transmission path is viewed from RT2, receiving data line 5,
It is composed of a transmission data line 6 and a clock line 7.

In the remote device, the transmission lines 3 and 4 are duplicated, whereas (2) RT2 is single-layered, so a selection circuit (abbreviated as SEL) is used to select one of the duplicated transmission lines. ) 8, 9 is a terminal, and 10 is a control circuit, which controls the terminal 9 and the exchange of control information between the HO8T1 and the control circuit 10. Usually, this control circuit employs a program control method. Recently, this program control method has been implemented using microcomputers. 11 is an interface circuit that controls sending data from the terminal 9 and data from the control circuit 10 to the transmission path 3 or 4, and vice versa.

In such a system, the dependent synchronous transmission and transmission path selection method on the RT2 side will be described. FIG. 2 shows an example of the internal configuration of RT2. In FIG. 2, 51 is a microcomputer (abbreviated as microcomputer), 52 is a read-only memory for storing programs, 53 is a random access memory for storing temporary data, 54 is a decoder for specifying each device, and 55 is a decoder for specifying each device. Clock generation for the microcomputer (3) The clock generator 56 is a phase generation circuit that generates the lock phase required by the microcomputer. Since these are general-purpose components and can be configured using well-known techniques, their explanations will be omitted. Further, 57 is a selection circuit (2-1) for selecting - of the double transmission path, and does not require any particular explanation. Reference numeral 58 denotes a data extraction circuit, which extracts the data sent from the HO8TI to its own RT2 from the reception transmission path 59 at a time position previously assigned to its own RT2, as described above. 60 is the opposite, from R'r2 to H at the above time position.
This is a circuit that inserts data to O8TI into the transmission transmission line 61. These sent and received data are transmitted through the sending and receiving transmission lines 59 and 61.
It is subordinate to synchronization. That is, it is synchronized with the clock 62 sent from HO8TI. On the other hand, RT2's microcontroller 5
1 is a clock generation source 5 different from the clock 62 on the transmission line side.
It is operated by the clock from 5. Therefore, the data from the microcomputer 51 and the data sent to the transmission path are not synchronized, that is, they are asynchronous. This reverse data flow is similarly asynchronous. The device that absorbs this (4) asynchronization is the 63 synchronization circuit.

As an example of the configuration of the synchronous circuit 63, a circuit using a memory that operates using two types of clocks, in this example, a clock on the microcomputer 51 side and a clock on the transmission line side, is used, but such a circuit requires a large amount of hardware. Not only that, but its control circuit is also complicated. Reference numeral 64 denotes an interface circuit that controls the connection between the synchronization circuit 63 and the microcomputer 51 described above.

Next, a selection circuit for selecting one of the duplicated transmission lines will be explained. FIG. 3 shows an example of the selection signal line and its timing signal sent from the HO8T side 1 or the sub-monitoring device to each RT. In FIG. 3, 80 is a signal indicating the selection instruction of the O system (or 1 system);
1 is an RT device designation signal, and 82 is a strobe signal. In FIG. 2, a system switching circuit 65 is an example of a circuit that receives these signals and performs system selection. The switching circuit 65 is ANDed with a flip-flop 66 that latches the system designation signal.
It is composed of a circuit 67 and an OR circuit 68, and its operation is clear (5) as can be seen from the drawing, so a description thereof will be omitted. Based on instructions from the switching circuit 65, the selection circuits 57 and 58 select one of the transmission paths. In addition, in FIG. 2, a clock disconnection due to a transmission line failure in the active system, such as a disconnection of the transmission line, is detected by a clock disconnection detection circuit 69, and a circuit for connecting the other transmission line and a microcomputer 5
The circuit that initializes the value 1 is also included.

As described above, in the conventional technology, not only the amount of hardware required to absorb asynchronization is large, but also the control thereof is complicated and the number of development steps is large, so that only an uneconomical system can be realized.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an economical system switching system.

[Summary of the invention]

In order to achieve the above object, the system switching method of the present invention operates the control device using a clock supplied from the transmission,
When a transmission path switching instruction is received, the clock of the transmission path before switching is continued to be supplied to the control device for a certain period of time, and after the control device completes one operation, the control device is stopped and the other transmission path is switched. After the clock from the switched transmission line becomes stable, the control device is restarted from the operation following the stopped operation.

[Embodiments of the invention]

The present invention will be explained below using an embodiment shown in FIG.

FIG. 4, like FIG. 3, is an example in which the present invention is applied to a program control type device using a microcomputer. Each part will be explained below.

151 is a microcomputer, 152 is a read-only memory, 153 is a random access memory, and 154 is a decoder, which is the same as the conventional one shown in FIG.

Reference numeral 156 denotes a phase generation circuit that generates a lock phase as required by the microcomputer, and has a similar configuration to the phase generation circuit 56 shown in FIG. The difference between these is that the conventional device shown in 2nd Wi receives the clock from the independent clock generator 11ii 155, whereas the present invention uses the clock sent from HO3TI as input.

That is, the operation of the microcomputer 151 is (7) synchronized with the clock of the transmission line. Therefore, the present invention does not require the synchronization circuit 63 that synchronizes the output data from the microcomputer 151 with the clock of the transmission line and sends it to the transmission line as in the prior art. 157 is a (2-1) selection circuit, 158 is a data extraction circuit, 159 is a reception transmission line, 160 is a data insertion circuit, +61 is a transmission transmission line, and 162 is a clock transmission line.

Since this is the same as that shown in FIG. 2, the explanation will be omitted.

Next, a transmission line selection method, ie, a system switching method, in this embodiment will be explained. If the transmission line is switched using the conventional method and the clock from the transmission line is thereby supplied to the microcomputer 151, the following problem will occur. Image transmission line clock 1
62 do not necessarily match, including the phase. This is obvious if you consider that if the cable length of the clock transmission path 162 is different, a difference in propagation delay will occur, resulting in a phase difference. In addition, selection instructions from the HO8Tl side or monitoring equipment are not always sent in synchronization with the clock of the transmission line. Therefore, when the selection instruction (8) switches the transmission line, the microcomputer is sent from the transmission line. 151
In the clock supplied to the other side, clock cracks, deviations, duty fluctuations, etc. occur. Due to this clock abnormality, the microcomputer 151 is no longer able to execute instructions normally, resulting in a runaway, that is, a system down. In order to prevent this, the following method is adopted in this embodiment.

Reference numeral 165 shows a configuration example of a system switching circuit. It is also assumed that the interface for external selection instructions is the same as that shown in FIG. Next, the operation of the switching circuit 165 will be explained. Selection instruction signal (A/5) 80, device instruction signal (E
N) 81 and the strobe signal (STB) 82 are received at the timing shown in FIG.
Set 6 and 167. flip flop 166
indicates that a system selection instruction has been activated, and flip-flop 167 indicates the system to be selected.

The output of the flip-flop 166 instructs the microcomputer 151 to stop and also starts the timer 168. At this point, the system has not yet been switched (9), so the microcontroller 1 uses the clock from the transmission line before switching.
The microcomputer 151 continues its operation, but since the stop instruction has already been issued, the microcomputer 151 stops after performing an l operation, that is, executing one instruction. At this point, the contents of the system to be selected held in the flip-flop 167 are transferred to the flip-flop 169 by the output of the timer 168, and at the same time, the system is switched by the output of the flip-flop 69. At this point, the microcomputer 151 remains stopped. After a while (2-1), the output clock of the selection circuit 157 becomes stable.At this point, the output clock of the selection circuit 157 becomes stable.
66 to release the stoppage of the microcomputer 151.

Since a stable clock has already been supplied to the microcomputer 151, the microcomputer resumes operation from the next instruction that was stopped. That is, even if the transmission path is switched, the microcomputer does not run out of control and continues to operate in synchronization with the clock of the transmission path.

164 is an interface circuit that connects the data extraction circuit 158 and data insertion circuit 16 to the microcomputer 164. Further, 170 is a clock disconnection detection circuit (10), which, like the prior art, switches the transmission path to another system and initializes the microcomputer 151 when a clock disconnection is detected.

〔Effect of the invention〕

According to the present invention, since the control device in the remote device operates in slave synchronization with the clock supplied from the HO3T device,
Not only is there no need for a synchronization circuit for exchanging data between the control devices on the transmission line, but there is also no need for a clock generation source to supply the control devices, leading to economical savings. Furthermore, since a synchronous circuit with complicated control is not required, the number of design steps can be shortened, and further economic efficiency can be achieved.

[Brief explanation of drawings]

Figure 1 is a diagram showing the configuration of a data transmission system between a duplicated parent device and a remote device, Figure 2 is a diagram showing the internal configuration of a conventional remote device using a microcomputer, and Figure 3 is a diagram showing the configuration of a data transmission system between a duplicated parent device and a remote device. FIG. 4 is a diagram showing the system selection signals sent to the device and their timing signals. FIG. 4 is a diagram showing the internal configuration of an implementation of a remote device to which the system switching method according to the present invention is applied. (II) 1...HO8T device, 2...Remote device, 3, 4...
・Transmission line, 5... Reception data line, 6... Transmission data line, 7... Clock line, 8... Selection circuit, 9...
Terminal, 1o... Control circuit, 11... Interface circuit, 51... Microcomputer, 52... Read-only memory, 53... Random access memory,
54... Decoder, 55... Clock generation source, 56
... Phase creation circuit, 57 ... (2-1) Selection circuit, 5
8... Data extraction circuit, 59... Reception transmission line, 60
...Data insertion circuit, 61...Transmission transmission line, 62.
...Clock transmission line, 63...Synchronization circuit, 64...
Interface circuit, 65... System switching circuit, 66...
・Flip-flop, 67...AND circuit, 68...
・OR circuit, 69... Clock disconnection detection circuit, 80...
- System selection signal, 81... Device designation signal, 82... Strobe signal, 151... Microcomputer, 1
52... Read-only memory, 153... Random access memory, 154... Decoder, 156... Phase creation circuit, 157... (2-1) Selection circuit, 158...
...Data extraction circuit, 159...Reception transmission line, 160
...Data insertion circuit, 161...Transmission transmission line, (1
2) 162...Clock transmission line, 164...Interface circuit, 165...System switching circuit, 166.167°169...Flip-flop, 168...Timer,
170... Clock disconnection detection circuit. (13)

Claims (1)

[Claims] In a program-controlled remote device that transmits and receives data to and from the master station in slave synchronization with the clock supplied from the master device, duplication between the master device and the remote device, including the clock line that transmits the clock and the data transmission and reception line. When performing system switching to select one of the transmission paths, after receiving a system switching signal from the parent device or another device, execute the program on the remote device in synchronization with the clock from the transmission path. After stopping the operation of the control device that is being executed after the command that is being executed is completed, switching the transmission path is executed, and after the clock from the transmission path after switching has become stable, the operation of the control device that is being executed is stopped again from the next command that stopped the control device. A system switching method characterized by executing