JP2630019B2 - Diagnostic path connection structure between diagnostic processor and device under diagnosis in information processing system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a diagnostic path connection structure between a diagnostic processor and a device to be diagnosed such as a main storage device, an input / output processing device, and an arithmetic processor in an information processing system.

[Conventional technology]

Under the control of a diagnostic processor, maintenance and diagnosis of each device constituting an information processing system such as a main storage device, an input / output processing device, an arithmetic processor, and a system control device connected to them have been conventionally performed. I have. In this type of information processing system, in order to send various diagnostic commands and the like from the diagnostic processor to each device to be diagnosed, and to send diagnostic result data and a failure occurrence report interrupt signal and the like from each device to be diagnosed to the diagnostic processor. Therefore, the diagnostic processor and each device to be diagnosed are connected by a diagnostic path.

Several structures have been proposed as connection structures of the diagnostic path between the diagnostic processor and each device to be diagnosed. One of the structures is one of the components of the information processing system and one of the devices to be diagnosed. A trip controller for the diagnostic processor is provided in the system controller which is also one of the two, and the trip controller and the diagnostic processor are connected by a diagnostic path. There is a structure in which a control unit is connected to another device to be diagnosed such as a main storage device, an input / output processing device, and an arithmetic processor by a one-to-one diagnostic path.

FIG. 2 is a block diagram of an information processing system employing such a diagnostic path connection structure. This information processing system includes a diagnostic processor 1, a system control device 2, a main storage device 3, an input / output processing device 4, and an arithmetic processor 5.
It is composed of

A diagnosis execution control unit 211 'is provided in the system control device 2 as a business trip control unit of the diagnosis processor 1. The diagnosis execution control unit 211' and the processor execution control unit 11 'in the diagnosis processor 1 are connected to a signal line l11. , l14 and l225 '. In addition, a port circuit 13 is provided in the diagnostic path as a switch for turning on and off according to the contents of the flip-flop 12. Here, a signal line l14 is a signal line for transmitting and receiving a diagnostic command, diagnostic result data, and the like, and a signal line l225 'transmits a failure occurrence report interrupt signal from the diagnostic execution control unit 211' to the processor execution control unit 11 '. Signal line for signal line l1
Reference numeral 1 denotes a signal line in which the signal lines l14 and l225 'are bundled.

Further, the diagnosis execution control unit 211 'and the storage control unit 22 in the system control device 2 are connected by a diagnosis path including a signal line l21, and the diagnosis execution control unit 211' and the main storage device are connected.
3, the input / output processing device 4 and the arithmetic processor 5 are signal lines
diagnostic path composed of l22, l26, l211; signal lines l23, l27,
They are connected by a diagnostic path composed of l212 and a diagnostic path composed of signal lines l24, l28, l213, respectively. A flip-flop 213 provided in the device diagnosis control unit 21 including the diagnosis execution control unit 211 'is a configuration control register corresponding to the main storage device 3, the input / output processing device 4, and the arithmetic processor 5, and each part 213a, Port circuits 215, 216, 21 which are switch means for turning on / off according to the contents of 213b, 213c
7 are connected in a diagnostic path between the diagnostic execution control section 211 'and the main storage device 3, the input / output processing device 4, and the arithmetic processor 5, respectively. Here, signal lines l26, l27, l28 are signal lines for transmitting and receiving diagnostic commands and diagnostic result data, etc.
The signal lines l211, l212, l213 are the main storage device 3, the input / output processing device 4,
A signal line for transmitting a fault occurrence report interrupt signal from the arithmetic processor 5 to the diagnosis execution control unit 211 ';
2, l23, l24 are signal lines that bundle them. The signal line l21 includes a signal line for transmitting and receiving a diagnostic command, diagnostic result data, and the like, and a signal line for transmitting a failure occurrence report interrupt signal from the storage control unit 22 to the execution control unit 211 '. The failure report interrupt signal output from the main storage device 3, the input / output processing device 4, the arithmetic processor 5, and the storage control unit 22 is compared with its own failure report interrupt signal in the diagnosis execution control section 211 '. The signals are combined in a logical OR manner and sent to the diagnostic processor 1 as a failure report interrupt signal.

In an information processing system employing such a diagnostic path connection structure, various operations associated with maintenance and diagnosis are performed under the control of the diagnostic processor 1. For example, in the case of the initialization processing, the following operation is performed. The diagnosis processor 1 is initialized by setting the flip-flop 12 to "0" via the signal line l12 to turn off the port circuit 13 and invalidate the diagnosis path between the diagnosis processor 1 and the diagnosis execution controller 211 '. This is performed in a state where intrusion of disturbance is suppressed.

The diagnostic processor 1 that has completed its initial setting process sets “1” in the flip-flop 12 and sets the diagnostic execution control unit 21.
Enable the diagnostic bus between 1 'and the system controller 2,
For example, the main storage device 3, the input / output processing device 4, and the arithmetic processor 5 start initialization processing in that order, for example.

In the process setting process of the system control device 2, first, the port circuits 215 to 217 are turned off by setting "0" to all the parts 213a to 213c of the flip-flop 213, and the intrusion of disturbance from the other devices 3 to 5 is performed. In this state, the diagnosis execution control unit 211 'first performs an initialization process. Next, by using the diagnosis execution control section 211 'that has completed the initialization processing, an initialization processing for the storage control unit 22, which is another unit in the system control device 21, is performed through a diagnosis path (l21) therebetween. Do through.

When the initialization processing of the system control device 2 is completed, the diagnostic processor 1 next proceeds to the respective parts 2 of the flip-flop 213.
By sequentially setting 13a, 213b, and 213c to "1", the diagnostic path between the main storage device 3, the input / output processing device 4, and the arithmetic processor 5 is sequentially activated, and the activated path The initialization process of each of the devices 3, 4, and 5 is performed using the diagnosis execution control unit 211 'via the.

In addition to the above-described initialization processing, the diagnostic processor 1 also performs diagnosis of each device using a diagnostic command, a failure process when a failure occurs, and the like. Here, as described above, the failure processing is performed by the failure occurrence report interrupt signal generated by the main storage device 3, the input / output processing device 4, the arithmetic processor 5, the storage control unit 22, and the diagnosis execution control unit 211 '. By being input as an interrupt signal to the unit 11 ', the currently executing process is interrupted and executed.

[Problems to be solved by the invention]

Conventionally, the above-described diagnostic path connection structure is adopted, and the diagnostic processor 1 only needs to have a diagnostic path, that is, a diagnostic interface only with the diagnostic execution control unit 211 'which is a business trip control unit. There is an advantage that the present invention can be used for various information processing systems without being limited to the information processing system. That is, as the type of information processing system, there are various systems having different numbers of processors such as a single processor system and a multiprocessor system, and there is also a system having a special storage device such as an extended storage device like a supercomputer system. Therefore, the number of devices to be diagnosed for maintenance and diagnosis is not constant. Therefore, the diagnosis processor 1 and each device to be diagnosed are
According to the structure connected by one-to-one diagnostic paths, the number of diagnostic paths (diagnostic interfaces) to be provided in the diagnostic processor 1 is not constant, so that it is difficult to generalize the diagnostic processor 1. According to the above, one diagnostic interface with the diagnostic execution control unit 211 'is sufficient.

By the way, the diagnostic path connection structure shown in FIG. 2 has an advantage that the diagnostic processor 1 can be general-purposed, but has the following problems.

Diagnosis execution control unit which is a business trip control unit of the diagnosis processor 1
Since the power supply 211 'is provided in the system control device 2 which is one of the devices to be diagnosed, the power supply control of the diagnosis execution control unit 211' is not common to the power supply of the diagnosis processor 1. For this reason, in the configuration control, the diagnosis execution control unit 211 'in the system control device 2 cannot be distinguished from the storage control unit 22, which is another unit to be diagnosed.
When 1 'is enabled, the storage control unit 22 is also enabled, and a signal such as an interrupt signal can freely jump from the storage control unit 22 into the diagnosis execution control unit 211' via the diagnostic path (l21). . Therefore, the diagnostic processor 1 cannot access only the diagnostic execution control unit 211 'as desired. In particular, if a fixed failure has occurred in the storage control unit 22, for example, during the initialization processing of the diagnosis execution control unit 211 ', the failure occurrence report interrupt signal causes the diagnosis path (l2
1) is input to the diagnostic execution control unit 211 'via the first processor, and is transmitted to the diagnostic processor 1. The diagnostic processor 1 interrupts the initial setting process and starts the fault process. become unable.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a purpose of the present invention is to provide a configuration in which a business trip control unit provided in a system control device can be prevented from entering a disturbance from another unit to be diagnosed in the device. Another object of the present invention is to provide a diagnostic path connection structure between a diagnostic processor and a device to be diagnosed in an information processing system employing the above.

[Means for solving the problem]

In order to achieve the above object, a diagnostic path connection structure between a diagnostic processor and a device to be diagnosed in the information processing system according to the present invention is provided with a business trip control unit of the diagnostic processor inside the system control device. And the diagnostic processor are connected by a diagnostic path, and the travel control unit and other devices to be diagnosed such as a unit to be diagnosed and a main storage device in the system controller are connected in a one-to-one diagnostic path. In the processing system, a first control information holding unit for holding first control information, and a diagnosis path provided to connect the unit to be diagnosed in the system control device and the business trip control unit one-to-one, A first switch for turning on and off in accordance with the held first control information; a second control information holding unit for holding second control information; A second switch provided in a diagnosis path for connecting to the business trip control unit and turned on and off in accordance with the held second control information; and a third control for holding third control information. Information holding means, provided in a diagnostic path connecting the business trip control unit and the another device to be diagnosed on a one-to-one basis, and turned on in accordance with the held first control information and third control information; , And third switch means for turning off.

Further, a failure occurrence report interrupt signal transmitted from the unit to be diagnosed in the system control device and the other device to be diagnosed through the diagnostic path connected one-to-one to the business trip control unit is transmitted to the first and the second devices. A first read-only path that bypasses third switch means and supplies to the business trip control unit; and a fault occurrence report interrupt signal sent from the business trip control unit via a diagnostic path connected to the diagnostic processor. And a second read-only path for supplying a fault occurrence report interrupt signal on the first read-only path to the diagnostic processor by bypassing the second switch means.

[Action]

In the diagnostic path connection structure between the diagnostic processor and the device to be diagnosed in the information processing system of the present invention, the first
Control information holding means holds the first control information, and makes a one-to-one correspondence between the unit to be diagnosed and the business trip control unit in the system controller.
The first switch means provided in the diagnostic path connected to the first switch turns on and off according to the held first control information.

Further, the second control information holding means holds the second control information, and the second switch means provided in the diagnostic path connecting the diagnostic processor and the business trip control unit includes the second control information. On and off in accordance with the control information, the third control information holding means holds the third control information,
A third switch provided in a diagnostic path connecting the business trip control unit and another device to be diagnosed on a one-to-one basis is turned on in accordance with the held first control information and the third control information.
Turn off.

Further, a first read-only path is a fault occurrence report interrupt signal transmitted from a unit to be diagnosed in the system control device and another device to be diagnosed via a diagnostic path connected one-to-one to the business trip control unit. Is supplied to the business trip control unit bypassing the first and third switch means, and a second read-only path is sent from the business trip control unit via the diagnostic path connected to the diagnostic processor. An interrupt signal and a fault occurrence report interrupt signal on the first read-only path are supplied to the diagnostic processor bypassing the second switch means.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. The information processing system shown in FIG. 1 includes a diagnostic processor 1, a system control device 2, a main storage device 3, an input / output processing device 4, and an arithmetic processor 5.

The diagnostic processor 1 includes a system control device 2, a main storage device
3, a processor that performs initial setting, configuration control, and maintenance diagnosis control including fault processing for the input / output processing device 4 and the arithmetic processor 5.

A processor execution control unit 11 provided in the diagnostic processor 1 is a control unit that executes a maintenance diagnostic program for the system control device 2, the main storage device 3, the input / output processing device 4, and the arithmetic processor 5, and controls the signal line l11. Through port circuit 13
Is connected to the diagnostic interface.

The port circuit 13 is a switch circuit that controls connection / disconnection of a diagnostic path between the processor execution control unit 11 and the device diagnostic control unit 21 inside the system control device 2. The port circuit 13 is connected to the processor execution control unit 11 by a signal line l11.
Is connected to the device diagnostic control unit 21 by signal lines l14 and l225 ', and when the content of the flip-flop 12 input by the signal line l13 is "1", the connection state is set, and the signal line l11 is set. And the signal lines l14 and l225 'are connected. When the content of the flip-flop 12 is “0”, the signal line l1
1 is disconnected from the signal lines l14 and l225 '.

The flip-flop 12 is a 1-bit flip-flop that is set or reset by the processor execution control unit 11 via the signal line l12.

Next, the system control device 2
And a storage control unit 22. The storage control unit 22 is a unit that controls memory access from the input / output processing device 4 and the arithmetic processor 5 to the main storage device 3.
It is connected to the main storage device 3, the input / output processing device 4, and the arithmetic processor 5 by data / control signal lines via signal lines l222, l223 and l224.

The device diagnostic control unit 21 decodes a diagnostic command sent from the diagnostic processor 1 via the signal line 114 and performs maintenance diagnosis of the storage control unit 22, the main storage device 3, the input / output processing device 4, and the arithmetic processor 5. It is.

The diagnostic execution control unit 21 decodes the maintenance diagnostic command sent from the diagnostic processor 1 and sends diagnostic data to the specified device or unit to be diagnosed, or receives diagnostic result data from the device to be diagnosed and sends it to the diagnostic processor 1. send.
Further, it receives an interrupt signal such as a failure report from each of the devices to be diagnosed and the unit, and notifies the diagnostic processor 1 of it. The diagnosis execution control unit 211 is connected to the port circuits 214, 215, 216 and 217 via signal lines l21, l22, l23 and l24, and performs maintenance diagnosis of the storage control unit 22, the main storage device 3, the input / output processing device 4, and the arithmetic processor 5, respectively. Is possible. Further, as described above, the diagnostic circuit 1 is connected to the port circuit 13 by the signal lines l14 and l225 '.

The port circuits 214, 215, 216, and 217 are switch means on a diagnostic path corresponding to the storage control unit 22, the main storage device 3, the input / output processing device 4, and the arithmetic processor 5, respectively.
It is almost the same as

The port circuit 214 is connected to the diagnostic execution control unit 21 by a signal line l21.
1 and storage control unit 2 via signal lines l25 and l210.
When the content of the flip-flop 212 input through the signal line l218 is "1", the connection state is set, and the signal line l21 is connected to the signal lines l25 and l210. When the content of the flip-flop 212 is "0", the signal line l21 is disconnected from the signal lines l25 and l210.

The port circuit 215 is connected to the diagnostic execution control unit 21 by a signal line l22.
1 and connected to the main storage device 3 by signal lines l26 and l211. The contents of the bit of the portion 213a of the flip-flop 213 input by the signal line l219 and the flip-flop 212 When the contents are both "1", the connection state is set, and the signal line l22 is connected to the signal lines l26 and l211. When either the bit of the portion 213a of the flip-flop 213 or the content of the flip-flop 212 is "0", the signal line l22 and the signal lines l26 and l211 are disconnected.

The port circuit 216 is connected to the diagnostic execution control unit 21 by a signal line l23.
1 and the input / output processor 4 via signal lines l27 and l212.
When the contents of the bit of the portion 213b of the flip-flop 213 input by the signal line l220 and the contents of the flip-flop 212 input by the signal line l218 are both "1", the connection state is set. The signal line l23 is connected to the signal lines l27 and l212. When either the bit content of the portion 213b of the flip-flop 213 or the content of the flip-flop 212 is “0”, the signal line l23 and the signal lines l27 and l212 are disconnected.

The port circuit 217 is connected to the diagnostic execution control unit 21 by a signal line l24.
1 and the arithmetic processor 5 via signal lines l28 and l213.
When the contents of the bit of the portion 213c of the flip-flop 213 input through the signal line l221 and the contents of the flip-flop 212 input through the signal line l218 are both "1", the connection state is set. The signal line l24 is connected to the signal lines l28 and l213. When either the bit content of the portion 213c of the flip-flop 213 or the content of the flip-flop 212 is "0", the signal line l24 and the signal lines l28 and l213 are disconnected.

The flip-flop 212 is a 1-bit flip-flop that is set or reset by the diagnosis execution control unit 211 via the signal line l214.

The flip-flop 213 is a 3-bit flip-flop composed of portions 213a, 213b, and 213c.
It is also a configuration control register corresponding to the input / output processing device 4 and the arithmetic processor 5. The flip-flop 213 is set or reset by the diagnostic execution control unit 211 via signal lines l215, l216 and l217, and its output is connected to the port circuits 215, 216 and 217 as described above, and is shown in FIG. However, they are sent to the storage control unit 22 and are used to control connection / disconnection of the signal lines l222, l223 and l224, respectively.

Next, the transmission path of the failure occurrence report interrupt signal in the diagnostic path will be described.

The failure occurrence report interrupt signal sent from the storage control unit 22 is input as an interrupt signal to the diagnosis execution control unit 211 via the signal line l210, the port circuit 214, and the signal line l21, and is also input to the signal line l210. The data is bypassed through the port circuit 214 by the connected read-only path l230 and input to the diagnosis execution control unit 211. This path l230 is literally a read-only path, and the diagnosis execution control unit 211 does not handle it as an interrupt signal.

Similarly, the failure occurrence report interrupt signal sent from the main storage device 3, the input / output processing device 4, and the arithmetic processor 5 includes the signal line l211, the port circuit 215, the signal line l22, the signal line l212, the port circuit 216, and the signal The diagnostic execution control unit 21 is connected via the line l23, the signal line l213, the port circuit 217, and the signal line l24, respectively.
1 as an interrupt signal and signal lines l211, l21
The input is bypassed by the port circuits 215, 216, and 217 by the read-only paths l231, l232, and l233 connected to the diagnosis execution control unit 211. This read-only path l231, l23
Diagnosis execution control unit 21
1 is not treated as an interrupt signal.

In the diagnosis execution control unit 211, each port circuit 214, 215, 216, 2
A signal a, which is a logical OR combination of a fault report interrupt signal added from 17 via the signal lines l21, l22, l23, and l24 and the fault report interrupt signal of the diagnostic execution control unit 211 itself, and each read-only signal. A total of five signals including the failure report interrupt signal added via the paths l230, l231, l232, and l233 are output to different signal lines in the signal line l225. The signal a generated by the diagnostic execution control unit 211 among the signals transmitted on the signal line l225
Is input as an interrupt signal to the processor execution control unit 11 via the signal line l225 ', the port circuit 13, and the signal line l11, and the read-only path l10 connected to the signal line l225'.
The signal is input to the processor execution control unit 11 via one of the signal lines. Further, the remaining fault occurrence report interrupt signals transmitted on the signal line l225 are input to the processor execution control unit 11 via different signal lines in the read-only path 110. This path 110 is literally a read-only path, and the processor execution control unit 11 does not handle it as an interrupt signal.

Since the present embodiment employs the diagnostic path connection structure as described above, the diagnostic processor 1
The diagnostic execution control unit 211 and the storage control unit 22, the main storage device 3, the input / output processing device 4, and the arithmetic processor 5 can be invalidated. Therefore, if the diagnosis execution control unit 211 is accessed via the diagnosis path in this state, the diagnosis execution control unit 211 is not affected at all by the disturbance, and the storage control unit 22 has a fixed failure and the failure occurrence report interrupt signal is output. Even if it does, the diagnostic processor 1 can execute the initial setting process of the diagnostic execution control unit 211 without receiving the interruption. In the present embodiment, the output of the flip-flop 212 is input not only to the port circuit 214 but also to the other port circuits 215 to 217, but this is so that all the port circuits can be turned off collectively. It is. Only the other port circuits 215 to 217 are flip-flop 21
Since it can be turned off depending on the content of 3, the output of the flip-flop 212 may be input only to the port circuit 214.

Further, in a state where all the port circuits 13, 214 to 217 are turned off, the storage control unit 22, the main storage device 3, the input / output processing device 4, the arithmetic and logic unit 4 in the system controller 2 are controlled by the read only paths l230 to l233 and the read only path l10. Since it is possible to recognize whether or not a failure has occurred in the processor 5, it is determined whether or not a failure has occurred before performing the initialization processing of the storage control unit 22 and each of the devices 3 to 5. If there is any device, the initialization process can be terminated to prevent execution of useless processing.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various other modifications can be made. The device to be diagnosed is not limited to the illustrated device, but may include another device such as an extended storage device. Further, the unit to be diagnosed in the system controller may include not only one storage control unit but also a unit of the same type or another type.

〔The invention's effect〕

As described above, according to the diagnostic path connection structure between the diagnostic processor and the device to be diagnosed in the information processing system of the present invention, the diagnostic path connecting the business trip control unit and the unit to be diagnosed in the system control device is By turning off the first switch means provided in the system control device, it is possible to suppress the intrusion of disturbance from the unit to be diagnosed in the system control device into the business trip control unit. Therefore, the diagnostic processor can safely access only the business trip control unit, and a failure occurrence report interrupt signal is output from the diagnosed unit having a fixed fault or the like during the initialization process of the business trip control unit by the diagnostic processor. Is transmitted to the diagnostic processor and the initialization process can be prevented from being interrupted. When the system control device includes a business trip control unit and a plurality of units to be diagnosed, the business trip control unit and each of the units to be diagnosed are connected in a one-to-one diagnostic path, and a first switch is provided during each diagnostic path. Means are provided, so that the maintenance diagnosis processing including the initialization processing of each unit to be diagnosed in the system control device can be divided and executed.

Further, a third switch means provided in each diagnostic path connecting the business trip control unit provided in the system control apparatus and another device to be diagnosed on a one-to-one basis is a third switch functioning as a system configuration register. By controlling not only the contents of the control information holding means but also the contents of the first control information holding means for controlling the first switch means, the content of the first control information holding means is connected to the business trip control unit. Diagnostic paths between all of the units to be diagnosed and the devices to be diagnosed can be invalidated collectively.

Further, the first read-only path and the second read-only path allow the diagnostic processor to read the status of the fault occurrence report interrupt signal from each unit to be diagnosed and each device to be diagnosed with each diagnostic path being invalidated. It becomes possible. Therefore, for example, prior to executing the initial setting process of the unit to be diagnosed or the device to be diagnosed, the existence of a failure of each unit to be diagnosed or each device to be diagnosed is checked, and the execution of useless initial setting process is omitted. Operation becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention, and FIG. 2 is an explanatory diagram of a conventional diagnostic path connection structure. In the drawing, 1... Diagnostic processor 2... System control device 3... Main storage device 4... Input / output processing device 5 ... arithmetic processor 11 ... processor execution control unit 12. Flip-flop to be configured 13 Port circuit configuring second switch means 21 Device diagnostic control unit 22 Storage control unit 211 Diagnosis execution control unit 212 Configured first control information holding means Flip-flop 213... Flip-flop 214 forming third control information holding means. Port circuits 215 to 217 forming first switch means. Port circuits l21, l25, and L210 forming third switch means. ... Signal lines l11, l14, l225 ′ constituting a first diagnostic path. Signal lines l22, l26, l221, l23, l27, l212, l24, l28, l213 constituting a second diagnostic path. Signal lines that make up the three diagnostic paths

Claims (2)

(57) [Claims] 1. A trip controller for a diagnostic processor is provided inside a system controller, the trip controller and the diagnostic processor are connected by a diagnostic path, and the trip controller and a unit to be diagnosed in the system controller are provided. A first control information holding unit for holding first control information, wherein the first control information holding unit holds first control information; A first, which is provided in a diagnostic path connecting the unit to be diagnosed and the business trip control unit on a one-to-one basis, and which is turned on and off in accordance with the held first control information.
Switch means; second control information holding means for holding second control information; and a second control information provided in a diagnostic path connecting the diagnostic processor and the business trip control unit. Second switching means for turning on and off according to the following, third control information holding means for holding third control information, and one-to-one connection between the business trip control unit and the another device to be diagnosed. A third switch provided in the diagnosis path and turned on and off according to the held first control information and third control information.
A diagnostic path connection structure between a diagnostic processor and a device to be diagnosed in an information processing system, comprising: 2. A fault occurrence report interrupt signal transmitted from a unit to be diagnosed in the system control device and another device to be diagnosed via a diagnostic path connected one-to-one to the business trip control unit. A first read-only path for bypassing first and third switch means and supplied to the business trip control unit; and a fault occurrence report sent from the business trip control unit via a diagnostic path connected to the diagnostic processor. 2. A second read-only path for supplying an interrupt signal and a failure occurrence report interrupt signal on the first read-only path to the diagnostic processor by bypassing the second switch means. A diagnostic path connection structure between a diagnostic processor and a device to be diagnosed in the information processing system described in the above.