JPH03228164A - Scsi bus extension system - Google Patents

Abstract

PURPOSE:To extend the cable length of an SCSI bus by connecting a bus control part which controls two SCSI buses between the SCSI buses. CONSTITUTION:When a host computer 1 sends the ID number 5 of an SCSI bus control part 3 to the SCSI bus 2, the SCSI bus control part 3 recognizes the fact that its own part is selected by the ID number on the SCSI bus 2, and sends the ID number 5 to the SCSI bus 4. A disk drive controller 5 recognizes the fact that its own is selected by the ID number on the SCSI bus 4 and issues a response, thereby, data transfer between the host computer 1 and the disk drive controller 5 can be performed setting the SCSI bus control part 3 as a relay point. Thereby, it is possible to extend the cable length of the SCSI bus.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a SCSI bus expansion method, and particularly to a SCSI bus expansion method provided with a bus control section.

[Conventional technology]

There are two types of conventional signaling systems using the 5csr bus: unbalanced type and balanced type. This unbalanced type has an open collector output and is active LOW ("L" - true), and the balanced type uses two trees for one signal, a child signal and one signal, and the level of the child signal is the same as that of one signal. This method recognizes it as true when it becomes higher than the level. The main differences between the two are signal pin assignment and maximum cable length (6 m for unbalanced type,
Currently, unbalanced SCSI bus signaling is more common than balanced.

An example of reading data on such a conventional SCSI bus will be explained with reference to FIG.

FIG. 3 is a 5C5I bus system configuration diagram for explaining an example of such a conventional system.

As shown in FIG. 3, for example, a host computer (initiator) 1 connected to the SCSI bus 2 wins arbitration for the right to use the SCSI bus 2, and selects the disk drive controller 5 as a target. This enables data transfer via the bus 2 between the host computer 1 and the disk drive controller 5.Next, the disk drive controller 5 sends a signal to the host computer 1 requesting a data read command. Send out. Accordingly,
The host computer l is a disk drive controller 5
Send a data read command to. Further, the disk drive controller 5 transfers data from the disk drive 6 to the host computer 1. When this data transfer is completed, the disk drive controller 5 sends report information of the command execution result to the host computer 1, and then sends a command completion message to end the reading. In addition, disk drive 6
When using the tape drive 8 instead, the tape drive controller 7 or similar processing is performed.

[Problem to be solved by the invention]

The above-mentioned conventional SCSI bus system has a drawback in that the 5CSI bus cable length is as short as 6 m in the single Endearad unbalanced type, as described above.

An object of the present invention is to provide a SCSI bus expansion method that can extend the length of such a bus cable.

[Means to solve the problem]

The SCSI bus expansion method of the present invention provides for a plurality of SCSI buses and two SCSI buses connected between the plurality of 5CSI buses.
In order to control the CSI bus, when one operates as a target, the other operates as an initiator, and is configured to extend the length of the SCSI bus cable.

〔Example〕

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

FIG. 1 is an SCS for explaining the first embodiment of the present invention.
It is an elliptic diagram of an I-bus system.

As shown in FIG. 1, this embodiment uses a host computer 1.
is connected to the first 5CSI bus controller 3 through the SCSI bus 2.
Further, a disk drive controller 5 is connected to the 5csr bus control section 3 through a SCSI bus 4. Further, the disk drive controller 5 is connected to the disk drive 6, and the tape drive controller 7 and the data drive 8 are the same as in the conventional example.

An example of reading data in such a bus system will be described below.

First, host computer (initiator) 1 is 5CS
Won the arbitration for the right to use the I-bus,
When the postcomputer 1 sends the ID number 5 of the 5C8I bus controller 3 to the SCSI bus 2, the SCSI bus controller 3 recognizes that it has been selected by the ID number on the 5C8I bus 2, and sends the ID number to the SCSI bus 4. Next, disk drive controller 5 sends out number 5, 5C8
Since the host computer 1 and the disk drive controller 5 recognize that they have been selected based on the ID number on the I bus 4 and respond, data transfer becomes possible between the host computer 1 and the disk drive controller 5 using the 5C8I bus control section 3 as a relay point. As a result, the disk drive controller I-roller 5
A signal is sent to request a data read command. SCSI bus control unit 3 that received this signal
transfers a signal to the host computer 1 to request a data read command. In response, the host computer 1 sends a data read command to the 5CSI bus control unit 3. SCSI received this
The bus control unit 3 transfers a data read command to the disk drive controller 5. In response to this read command, the disk drive controller 5 sends the data of the disk drive 6 to the SCSI bus control section 3, and the 5C8I bus control section 3, which receives this, transfers the data to the host computer 1. When this data transmission is completed, the disk drive controller 5 sends the SCS
Report information of command execution results is sent to the I bus control unit 3. Upon receiving this, the SCSI bus control unit 3 transfers report information of the command execution results to the host computer 1. Next, the disk drive controller 5
sends a command completion message to the 5C8I bus control unit 3. As a result, the SCSI bus control unit 3 transfers this message to the host computer 1, and the host computer 1 receives and accepts this message, thereby completing the data reading.

FIG. 2 is a 5C8 for explaining the second embodiment of the present invention.
It is an I bus system configuration diagram.

As shown in FIG. 2, this embodiment uses a host computer 1.
is connected to the SCSI bus control section 3 through the SCSI bus 2, and the SCSI bus control section 9 is connected to the SCSI bus control section 3 through the 5csr bus 4. The disk drive controller 5 is connected to the SCSI bus 10.
The disk drive controller 5 is connected to the disk drive 6 through the 5csr bus control section 9.

Hereinafter, an example of reading data will be explained similarly to the first embodiment described above.

First, when the host computer 1 (initiator) wins the arbitration and sends the ID number 5 of the 5C8I bus controller 3 to the 5csr bus 2, the SCSI bus controller 3 recognizes that it has been selected by the ID number on the 5C8I bus 2. and sends ID number 5 to 5C8I bus 4. Similarly, the 5C8I bus control unit 9
Since it recognizes that it has been selected by the ID number above, it sends the ID number onto the SCSI bus 10. Using this ID number on the SCSI bus 10, the disk drive controller 5 recognizes that it has been selected and responds. In this way, data can be transferred between the host computer 1 and the disk drive controller 5 using the 5C8I bus controllers 3 and 9 as relay points.

Next, the disk drive controller 5 sends a signal to the SCSI bus control unit 9 to request a data read command. The SCSI control unit 9 that received this transfers the received signal to the SCSI control unit 3. The SCSI control unit 3 that receives this signal transfers the received signal to the host computer 1. In response, the host computer 1 sends a data read command to the SCSI bus control section 3, and the SCSI bus control section 3 then transfers the received command to the 5C8I bus control section 9. Further, the SCSI bus control unit 9 transfers the received command to the disk drive controller 5. The disk drive controller 5 that received this command sends the data from the disk drive 6 to the SCSI bus control section 9, and the 5csI bus control section 9 that received this data sends this data to the SCSI bus control section 3. Forward. Further, the SCSI bus control unit 3 that has received and received this data sends the data to the host computer 1. When this data transfer is completed, the disk drive controller 5 sends report information of the command execution result to the SCSI bus control unit 9. Next, the 5CSI bus control unit 3 that received this transfer transfers a report of the result of the received command to the host computer 1. Next, the disk drive controller 5 similarly sends a message indicating the end of the command to the host computer 1, and finishes reading the data.

〔Effect of the invention〕

As explained above, the SCSI bus expansion method of the present invention allows the bus control unit that controls two SCSI buses to be
By connecting n target devices between the bus and the SCSI bus, the SCSI bus cable length can be extended to nx6 m.

[Brief explanation of drawings]

FIG. 1 is a 5cs diagram for explaining the first embodiment of the present invention.
r bus system elliptical diagram configuration FIG. 2 is a 5C8I bus system configuration diagram for explaining a second embodiment of the present invention, and FIG. 3 is a SCSI bus system configuration diagram for explaining a conventional example. 1...Host computer, 2.4.10...5C
8I bus, 3.9...5CSI bus control section, 5...
Disk drive controller, 6... Disk drive, 7... Tape drive controller, 8...
tape drive.

Claims (1)

[Claims] a plurality of SCSI buses; and a bus control unit connected between the plurality of SCSI buses and configured to operate the other as an initiator when one operates as a target in order to control the two SCSI buses; A SCSI bus expansion method characterized by extending the cable length.