JPH05298202A - Bus fault detection system - Google Patents

Abstract

PURPOSE:To instantaneously detect the omission of the cables and the bus relaying base boards by a bus master device for a bus which is relayed via these cavbles and base boards and defines the bus master device and a bus termination base board as its both ends. CONSTITUTION:A bus fault detecting signal line 140 is relayed via the cables 30 and 31-3n and the bus relaying base boards 21-2n and defines a bus terminaltion substrate 4 and a bus master device 1 as its initiation and termination respectively. Then the line 140 is pouned in the board 4 and pulled up via an R6 and an R8 at the precedent stages of the boards 21-2n and the receivers 10 and 7 of the device 1. A DET 5 detects a fact tha thte potential of the line 140 is changed to a high level from a low level when one of those cables, bus relaying base boards and bus termination base board is omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus failure detection method, and more particularly to a bus failure detection method for detecting a cable drop and a board drop of a bus relayed by a cable and a relay board.

[0002]

2. Description of the Related Art Conventionally, in this type of bus failure detection method, when a data transfer is actually performed through the bus and the transfer becomes unsuccessful, the failure is detected.

[0003]

In this conventional bus failure detection method, a bus failure cannot be detected until the bus transfer of data from the bus master apparatus through the portion where the cable is disconnected or the board is disconnected is detected, and the bus master apparatus is not detected. However, there is a problem that the failure processing is delayed because of lack of immediacy in detecting the failure.

[0004]

SUMMARY OF THE INVENTION A bus fault detection system of the present invention is a bus relayed via a plurality of cables and a plurality of bus relay boards and having a bus terminating board and a bus master device at both ends, the cable and the bus. Fault detection that is relayed via a relay board and grounded in the bus termination board with the bus termination board as the starting point and the bus master apparatus as the termination point It has a signal line.

The bus master device includes a change detection circuit for detecting that the potential of the fault detection signal line has changed from low level to high level.

[0006]

In the configuration of the present invention, when the cable, the bus terminating board, and the bus relay board are disconnected, the potential of the bus fault detection signal line changes from low level (earth) to high level (power) to cause a fault. Can be detected.

[0007]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a bus failure detection system of the present invention.

In this embodiment, a cable 30, a bus relay board 21, a cable 31, a bus relay board 2n, and a cable 3n are cascade-connected between the bus master device 1 and the bus termination board 4. Bus cables 30, 31 to 3
n has a bus signal line 13 and a fault detection signal line 14, and the fault detection signal line 14n is grounded at the input of the driver 14 in the bus termination board 4 at the starting end, and each bus relay board 2n, ...
Inside, there is a pull-up resistor (hereinafter R) in front of the receiver 10.
It is connected to the + 5V power source via 8 and pulled up, and connected via the receiver 10 and the driver 9 to the fault detection signal line to the bus relay board of the next stage. The fault detection signal line 140 of the driver 9 output of the bus relay board 21 is connected to the + 5V power source via R6 in the terminating bus master device 1 and pulled up, and via the receiver 7 the change detection circuit (hereinafter DET) 5 Connected with. In this embodiment configured as above, the cables 30, 31, to 3 are
When any one of n, the bus relay boards 21 to 2n, and the bus termination board 4 is removed, the signal at the input of the receiver 7 changes from the low level to the high level, and the DET 5 causes a failure due to this change. To detect.

[0009]

As described above, according to the present invention, by providing the fault detection signal line that is pulled up in each bus relay board and grounded in the bus termination board, the cable disconnection without the data bus transfer, This has the effect of enabling immediate detection of a failure of the board.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a bus failure detection system of the present invention.

[Explanation of symbols]

 1 Bus Master Device 21, ~ 2n Bus Relay Board 30, 31, ~ 3n Cable 4 Bus Termination Board 5 Change Detection Circuit (DET) 6,8 Pull-up Resistor (R) 7,10 Receiver 9,11 Driver 13 Bus Signal Line 140 , 141 to 14n Fault detection signal line

Claims (2)

[Claims] 1. A bus relayed via a plurality of cables and a plurality of bus relay boards and having a bus termination board and a bus master device at both ends, and a bus relayed via the cables and the bus relay board, A bus fault detection method characterized by being grounded in the bus terminating board with the bus master device as a start end and terminating with the bus master device, and the bus relay substrate and the bus master device have a fault detection signal line pulled up in a preceding stage of a built-in receiver. . 2. The bus fault detection method according to claim 1, wherein the bus master device includes a change detection circuit that detects that the potential of the fault detection signal line has changed from low level to high level.