JPH04293335A - Master station with backup function in transmission system - Google Patents

Abstract

PURPOSE:To prevent it in an inexpensive method that a function of other slave station receiving and utilizing a transmission data is stopped resulting from the stop of data transmission for a prescribed period from one slave station when a CPU of a master station is in system-down in a system that plural slave stations and the master station are connected to a common transmission line and the master station sends a transmission request command to the slave stations for a prescribed period through the transmission line. CONSTITUTION:A master station 1 is provided with a backup section 15 employing hardware logic and not using software which receives other power supply E2 than that for a CPU 11, detects a system-down of the CPU 11, throws a changeover switch 16 to a position of the backup section and outputs a transmission request command for a prescribed period to a transmission line 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission system in which a plurality of slave stations and a master station communicate via a common transmission line, and particularly to a master station equipped with a backup function in the event of an abnormality. In the following figures, the same reference numerals indicate the same or corresponding parts.

0002

2. Description of the Related Art FIG. 3 shows an example of the configuration of this type of data transmission system. In the figure, 1 is the master station, 2
(2-1, ~, 2-3) are slave stations #1 ~ #3, respectively, and 3 is a common transmission line that connects these master station 1 and each slave station 2-1, ~, 2-3. be. In such a transmission system, the master station 1 usually sends the request message R.
EQ is sent to slave station 2, and in response to this message REQ, a predetermined slave station 2 (#2 slave station 2-2 in the example in this figure)
Generally, the master station 1 returns a response signal ANS to the master station 1. In this case, master station 1
is always sent to each slave station 2-1, ~, at regular intervals.
2-3, a certain request message REQ is sent so as to return a certain type of response.

0003

[Problem to be Solved by the Invention] In the transmission system described above, if the master station 1 goes down, it will not send this request message REQ, and therefore no response will come from the slave station 2, causing the transmission system to go down. Resulting in. In order to avoid such a situation, duplication or triplexing of the master station 1 is being considered, but these systems are generally complicated and tend to be expensive. SUMMARY OF THE INVENTION An object of the present invention is to provide a master station with a backup function in a transmission system in an inexpensive manner so that the entire transmission system will not go down even if the master station goes down.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the master station with a backup function according to claim 1 provides a method for connecting a master station (such as 1) and a plurality of slave stations (such as 2) to a common Transmission line (3
etc.), and at least the master station sends, at a predetermined period, a predetermined request message (REQ) that specifies one or more predetermined slave stations among the slave stations and prompts them to transmit data in sequence. etc.) to the transmission line, the master station is separate from a main unit (such as the CPU 11) that executes predetermined operations including the above-mentioned operations, and is connected to at least a separate power source from this main unit. A backup means (such as E2) that detects an abnormality in this main body and sends the request message at the above-mentioned period without going through software.
15, etc.) and a switching means (selector switch 16, etc.) for switching the connection with the transmission line between the main body side and the backup means side,

In the master station with a backup function according to claim 2,
The master station with a backup function according to claim 1, wherein ``the switching means is automatically switched from the main body side to the backup means side based on an abnormality in the main body section'',

In the master station with backup function according to claim 3, in the master station with backup function according to claim 1, ``the switching means is manually switched'', and

[0007] In the master station with backup function according to claim 4, in the master station with backup function according to claims 1 to 3, ``the backup means generates a signal indicating whether or not there is an abnormality in the response of the slave station to the request message. (LE
D, etc.).

[0008]

[Operation] In the master station 1, there is provided a backup section 15 consisting of hard logic that does not use software and operates on an independent power source E2, separately from the main section consisting of the CPU 11 and the like. The backup unit 15 is assumed to output the same message as the periodic request message REQ, which prompts the slave station 2 to send data, which the main unit always sends, based on the abnormality detection signal for the main unit. When this abnormality occurs, the selector switch 16
The connection with the transmission line 3 is automatically or manually switched from the main unit side to the backup unit 15 side.

[0009]

Embodiment Next, an embodiment of the present invention will be described based on FIGS. 1 and 2. FIG. 1 is a block diagram showing the configuration of a master station as an embodiment of the present invention. In the figure, 11 is a CPU that controls this master station 1;
12 is an LSi that controls transmission via the transmission line 3;
13 is a MODE for modulating and demodulating communication data of the CPU 11;
M and 14 are line driver/receivers that are located between the MODEM 13 and the transmission line 3 and amplify the transmitted and received transmission signals, and E1 is a power supply for each of the above sections 11 to 14. Further, 15 is a backup section newly provided in the present invention, 16 is a changeover switch, and E2 is an independent power source for this backup section 15. The master station 1 is generally composed of 11 to 14 parts. Even if any part of these 11 to 14 goes down, the functions of the master station 1 will be lost. So C
If the PU 11 fails, the failure is detected by a watchdog timer (not shown), and failures in the parts 12 to 14 are detected by constantly looping back the transmission (that is, checking the transmission output).

The backup unit 15 receives the failure detection signal from the sections 11 to 14, switches the switch 16 to its own side, and performs a backup operation. This backup section 15 is configured to operate on parts 11 to 14, that is, the power supply E1 of the master station main body and a separate power supply E2, and enables backup operation even if the power supply E1 of the master station main body goes down. . In addition, this backup unit 15 does not use a CPU (software),
Consists of only discrete parts. Therefore, even if the CPU 11 goes out of control due to noise coming in from the transmission line 3, the backup operation can be performed reliably. The backup unit 15 also transmits to each slave station 2 only a certain request message REQ that the master station itself always transmits to the slave stations 2 . The function of transmitting such a certain message is easy to implement with a hard logic circuit, and the circuit reliability is high.

Although the backup unit 15 receives the response signal ANS from each slave station 2, it does not have a mechanism for displaying its value. However, it does have a mechanism that constantly checks whether the response is normal or not, and indicates whether it is normal or abnormal using an LED or the like. This is backup part 1
Since the necessary operation in section 5 is just a backup, the purpose is to reduce the number of parts in this section 15 and improve its reliability. In addition, the backup section 15 is connected from 11 to 1 as described above.
The switch 16 may be automatically switched to enter the backup operation upon receiving the abnormality signal of the sections up to 4, or the switch 16 may be switched to the backup section 15 side with human intervention.

FIG. 2 shows an example of a system configuration when the master station 1 of FIG. 1 is applied to an instrumentation system. In the figure, 3 is a two-wire transmission line, 2A is a transmitter as the slave station 2, and 2B is a controller that also controls the valve 20. In this two-wire transmission system, the controller 2B receives measured value data from the transmitter 2A, compares it with a set value in the controller 2B, operates the valve 20, and controls a certain physical quantity. Here, the transmitter 2A always returns a measured value as a response signal ANS to the master station 1 in response to the request message REQ from the master station 1.
At this time, the controller 2B receives the reply data from the transmitter 2A and uses it for control.

If the master station 1 were to go down, in the conventional case, the controller 2B would be unable to receive the measured value from the transmitter 2A, resulting in an uncontrollable state. However, in the present invention, even if the main unit of the master station 1 goes down, the backup unit 15 operates, so the measured value data of the transmitter 2A is transmitted by the controller 2B, and control continues. The backup unit 15 differs in function from the master station main body in that it cannot display slave data and cannot exchange messages other than the above-mentioned certain message data. However, it is possible to provide an inexpensive backup method and configure a highly reliable system.

[0014]

[Effects of the Invention] According to the present invention, the master station 1
and a plurality of slave stations 2 are connected to a common transmission line 3, and at least the master station 1 designates a predetermined one or more slave stations among the slave stations 2 at a predetermined period and sequentially , in a transmission system that sends a predetermined request message REQ requesting data transmission to the transmission line 3, the master station 1 has a main unit (
(CPU 11, etc.), a backup means 15 which is supplied with at least a power source E2 separate from the main body, detects an abnormality in the main body, and sends the request message REQ at the cycle without going through software; Since it is equipped with a changeover switch 16 for switching the connection with the transmission line 3 between the main body side and the backup means 15 side, backup of the transmission system in the event of an abnormality in the main body of the slave station is achieved in an inexpensive manner. things are possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a master station as an embodiment of the present invention.

[Fig. 2] System configuration diagram for explaining a specific operation example of the present invention

[Figure 3] General configuration diagram of transmission system

[Explanation of symbols]

1 Master station 2 (2-1, ~, 2-3, 2A, 2B) Slave station 2A Transmitter 2B Controller 3 Transmission line 11 CPU 12 Transmission control LSi 13 MODEM 14 Line driver receiver 15 Backup section 16 Changeover switch E1, E2 Power supply REQ Request message ANS Response signal (measured value)

Claims (4)

[Claims] Claim 1: A master station and a plurality of slave stations are connected to a common transmission line, wherein at least the master station specifies one or more predetermined slave stations among the slave stations at a predetermined period. In a transmission system that sequentially sends a predetermined request message to the transmission line to prompt data transmission, the master station is separate from a main unit that executes predetermined operations including the above-mentioned operations. , a backup means that is supplied with at least a power source separate from the main body, detects an abnormality in the main body, and sends the request message at the cycle without going through software, and a connection with the transmission line. A master station with a backup function in a transmission system, comprising a switching means for switching between a main body side and a backup means side. 2. The master station with a backup function according to claim 1, wherein the switching means is configured to automatically switch from the main body side to the backup means side based on an abnormality in the main body part. A master station with a backup function in a transmission system. 3. The master station with backup function in a transmission system according to claim 1, wherein said switching means is manually switched. 4. The master station with a backup function according to claim 1, wherein the backup means outputs a signal indicating whether or not there is an abnormality in the response of the slave station to the request message. Master station with backup function in transmission system.