JPH07141267A - Scsi bus controller - Google Patents

Abstract

PURPOSE:To make it possible to operate a target even if abnormality occurs, and to transmit bus trace information to a host so as to make judgement of a fault possible by providing two small computer system interface(SCSI) controllers which can operate even as an initiator and a target. CONSTITUTION:The SCSI controller 1 and SCSI device 3 which serve as the initiator and target are connected to each other by a SCSI control bus 11 and a SCSI data bus 12, and the SCSI controller 1 controls the SCSI device 3. If the SCSI device 3 can not be controlled owing to a fault of the SCSI controller 1, the stand-by SCSI controller 2 is operated to control the SCSI device 3. Further, the SCSI controller 1 is operated as the initiator and the SCSI controller 2 is operated as the target respectively, thereby the diagnostic test of the SCSI controllers using SCSI buses can be conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SCSI (Small Computer System Interface) bus controller, and more particularly to a SCSI bus control system in a computer system having a SCSI bus.

[0002]

2. Description of the Related Art A SCSI bus is defined as ANSI (American National Standard Institute) technical committee as ANSI X3.131-1986 as an interface bus for connecting a host computer and peripheral devices having various intelligent functions. ing.

In this SCSI bus, a device for sending a command is defined as an initiator, and a host computer or a SCSI controller provided separately usually serves as an initiator. A device that executes the command is defined as a target, and a CD-ROM drive unit or the like operates as the target.

In the conventional SCSI bus control system of this type, by connecting a target which is a variety of SCSI devices, a normal or abnormal diagnostic test of an initiator which is a SCSI controller is performed.

For example, Japanese Patent Laid-Open No. 2-239337 discloses a technique for testing a SCSI controller by simulating a diagnostic program assuming that a target is connected.

When operating the SCSI bus, the SCS
A technique of always storing data of the I bus in a memory is disclosed in, for example, Japanese Patent Laid-Open No. 2-002436.
In this technique, a SCSI bus monitor method is shown in order to monitor data on the SCSI bus.

In each of these prior arts, basically, as shown in FIG. 5, one initiator 1 is provided to control a plurality of targets 3.
In FIG. 5, reference numerals 11 and 12 denote a SCSI control bus and a SCSI data bus which connect the initiator 1 and the target 3, respectively, and 13 denotes a host bus which connects the host (not shown) and the initiator 1.

[0008]

This type of conventional SCS
In the I-bus control system, as shown in FIG. 5, the SCSI controller 1 operating as an initiator and the SCS
I controller 1 and SCSI device (target) 3
It is composed of the SCSI buses 11 and 12 that connect to each other. Therefore, when the SCSI controller 1 does not operate normally, the target 3 connected to the SCSI bus becomes uncontrollable.

However, in a computer system having a SCSI bus, even if an abnormality occurs in the SCSI controller operating as the initiator, the SCSI
It is necessary to operate the target SCSI device connected to the bus.

Further, since the trace information of various data flowing on the SCSI bus is not transmitted to the host bus, there is a problem that it is not possible to determine what kind of trouble has occurred.

Further, there is a problem that the status of the SCSI bus in operation cannot be visually confirmed.
There is also a problem that the SCSI bus test diagnosis cannot be performed unless the initiator and the target are aligned when determining whether the I controller is normal or abnormal.

Therefore, the present invention has been made to solve the above-mentioned drawbacks of the prior art. The purpose of the present invention is to enable operation of a target even if an abnormality occurs in the SCSI controller and to obtain bus trace information. SCSI that enables transmission to the host for fault determination, visual confirmation of bus status, and SCSI bus diagnostics at all times
It is to provide a bus control device.

[0013]

A SCSI bus controller according to the present invention comprises first and second SCSI controllers having an initiator function for issuing a command and a target function for executing this command, and the first and second SCSI controllers. SCSI data bus and SCSI control bus for connecting two SCSI controllers, storage means for sequentially storing each data flowing through the SCSI data bus and SCSI control bus, and status of the SCSI bus according to data flowing through the SCSI control bus It is characterized by including bus phase display means for displaying and a DMA controller for controlling direct memory access from the storage means to the host bus.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. The SCSI controllers 1 and 2, which also serve as initiators and targets, and the SCSI device 3 are connected by a SCSI control bus 11 and a SCSI data bus 12.

SCSI control bus 11 here
Is a BUSY line, SELECT as shown in FIG.
Line, RESET line, CONTROL / DATA
Line, INPUT / OUTPUT line, MESSA
GE line, REQUEST line, ACKNOWLE
It is composed of nine signal lines of DGE line and ATTENTION line, and the SCSI data bus 12 is composed of eight data lines DB0 to DB7 and one odd parity line DBp.

Normally, the SCSI controller 1 is operated as an initiator. In other words, SCSI controller 1
To control the SCSI device 3. Hello SCSI
If the SCSI device 3 cannot be controlled due to the failure of the controller 1, the spare SCSI controller 2
Is operated to control the SCSI device 3.

Further, even when the SCSI device (target) is not connected (FIG. 3) when judging whether the SCSI controller is normal or abnormal, the SCSI controller 1
Is used as the initiator and the SCSI controller 2 is operated as the target, it is possible to perform a diagnostic test of the SCSI controller using the SCSI bus.

Further, by operating the SCSI controller 1 as a target and the SCSI controller 2 as an initiator, the operation of the SCSI controller 2 as an initiator can be confirmed.

Furthermore, the SCSI bus trace controller 4 and the address controller 8 shown in FIG.
SI control bus 11 and SCSI data bus 12
Data sequentially flowing through the S
The data is written in the CSI bus trace memory unit 10 and the data is updated. It should be noted that the data in the SCSI bus trace memory unit 10 is never sent to the SCSI bus through the latch circuits 6 and 7. Further, the DMA controller 5 sweeps the data in the SCSI bus trace memory unit 10 onto the host bus 13 by DMA transfer. The data on the SCSI bus trace memory unit 10 is not rewritten by the data on the host bus 13.

In addition, a bus phase display section 9 is provided so that the state of the SCSI bus in operation can be visually confirmed. The bus phase display section 9 is a CONTROL / DATA line, IN in the SCSI control bus 11.
PUT / OUTPUT line, MESSAGE line,
When the five signal lines of the BUSY line and the SELECT line change to the values shown in FIG. 4, the respective SCSI bus phases are displayed.

For example, in the bus phase shown in FIG. 4, "bus free" represents a bus unused state, "arbitration" represents a bus contention state, and "selection" represents which target the initiator selects. “Data out” and “data in” represent the input / output state of data with reference to the initiator.

Further, "command" indicates a command transmission state from the initiator, and "status" indicates command normality / abnormality. These bus phases shown in FIG. 4 all comply with the above-mentioned ANSI regulations. It is a thing.

[0024]

As described above, according to the present invention, since two SCSI controllers that can operate as both an initiator and a target are provided, even if one SCSI controller fails, it can be connected to the bus. Existing SCSI controller can be operated by another SCSI controller, and the normality / abnormality of the SCSI controller can be judged by the bus diagnostic test by operating one target as the initiator and the other target as the target. is there.

Further, since the trace information of the data on the SCSI bus is transmitted to the host bus, there is an effect that the failure determination can be facilitated and the bus phase of the operating SCSI bus can be visually confirmed.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a SCSI bus.

FIG. 3 is a diagram for performing SCSI bus diagnosis without using a target.

FIG. 4 is a diagram showing a bus phase state of a SCSI bus.

FIG. 5 is a block diagram showing a conventional SCSI bus control system.

[Explanation of symbols]

 1, 2 SCSI controller 3 SCSI device 4 SCSI bus trace control unit 5 DMA controller 6, 7 latch circuit 8 address controller 9 bus phase display unit 10 SCSI bus trace memory unit 11 SCSI control bus 12 SCSI data bus 13 host bus

Claims (3)

[Claims] 1. A first function having an initiator function for issuing a command and a target function for executing the command
And a second SCSI controller, and S for connecting the first and second SCSI controllers
CSI data bus and SCSI control bus, storage means for sequentially storing each data flowing through the SCSI data bus and SCSI control bus, and bus phase display means for displaying the status of the SCSI bus according to the data flowing through the SCSI control bus And a DMA controller for performing direct memory access control from the storage means to the host bus. 2. The SCSI bus controller according to claim 1, wherein the first SCSI controller operates as an initiator and the second SCSI controller operates as a target. 3. The storage means includes a latch means for sequentially latching each data flowing through the SCSI data bus and the SCSI control bus, a memory for storing the latch contents of these latch means, a latch means for these and a memory. 3. The SCSI bus control device according to claim 1, further comprising a control means for controlling the.