JPH07160435A - Bus connection controller - Google Patents

Abstract

PURPOSE:To shorten a seek time by connecting plural devices which store the same recording contents for a SCSI device which has a slow seek time and selecting a device to be put in operation according to a sought address. CONSTITUTION:For a device A, the signal from a SCSI bus is connected to a device I/F 2 through bus connecting circuits 5a and 7, and also connected to a device B through bus connecting circuits 6a and 7 on a daisy chain basis. The signal of the bus connecting circuits 5b and 6b is a specific control signal of the SCSI bus. A bus converting and connecting circuit 7 is made possible to output a signal of AND among BSY, C/D, and REQ of the devices A and B onto the SCSI bus, outputs the ACK signal from the SCSI bus properly to respective devices according to the state of a disconnected device, and also outputs the signal of a data bus O even to a data bus 1 for the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus connection control device, and more particularly to a bus connection control device, which is used for accessing a SCSI device via a SCSI bus. The present invention relates to a connection control device.

[0002]

2. Description of the Related Art SCSI (Small Computer Systems Int)
erface: Scazi) is a standard interface for connecting peripheral devices that require high-speed data transmission with a personal computer. It is an extension of the function of the conventional standard, SASI, and has upward compatibility with SASI. Established in 1986 by ANSI (American National Standards Institute, Anthy). Specifically, it is an interface for connecting a hard disk device, an optical disk device, a CD-ROM, a laser printer, etc. to a personal computer.
You can connect up to 7 peripheral devices including hard disk ("Computer Glossary", Saitosha, 19
91,12,25, p.63-64).

In the prior art, there has been no switching of signals on the SCSI bus and connections between SCSI devices depending on the state of the SCSI bus. Further, there is a disk array device as a method of connecting a plurality of devices to speed up access to a disk. This disk array device simultaneously reads and writes data to a plurality of hard disks. For example, for writing,
A series of data to be written is divided into a plurality of data and written into a plurality of hard disks. For reading, conversely, the data written on a plurality of hard disks are combined into a series of read data, which is used as read data.

[0004]

As described above, in the conventional bus connection control device, for example, a CD-ROM,
Access time is high for MDs. For example, CD-RO
The average access time in M is about 200 ms at present, and about 500 ms in MD. These access times are extremely large values with respect to the processing speed of the CPU, which is a bottleneck in speeding up data processing.
Generally, the larger the moving range of the head is, the longer the access time is, and the seek range is improved by using a plurality of devices and sharing the seek ranges of the devices.

The disk array device is intended to speed up access by connecting a plurality of devices, but in order to realize it, in terms of hardware, a dedicated controller and hard disk, and data read from each device are stored. There is a problem in that the OS needs to be compatible with the disk array in terms of software such as a buffer memory to be installed.

The present invention has been made in view of the above circumstances, and is an apparatus having the same recorded contents as a SCSI apparatus having a slow seek time (time required to move to a place where reading or writing is performed). It is an object of the present invention to provide a bus connection control device in which a plurality of devices are connected to select a device that operates according to a seek address to shorten the seek time.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a bus used in a SCSI system including at least one initiator commanding an instruction and a plurality of targets receiving an instruction from the initiator. In the connection control device, the connection between the signal terminal on the target side can be changed based on the information in the SCSI phase from the initiator and the address information given in advance while being inserted between the initiator and the target. It is characterized in that it has a switching means.

[0008]

The bus connection control device according to the present invention has an interface to a SCSI bus and an interface to a plurality of SCSI devices.
Switches the connection between the CSI bus and multiple SCSI devices. Specifically, multiple SCSI recording devices with the same recorded contents are connected, the logical block address is detected by the data signal of the command phase given from the SCSI bus to this device, and the address given in advance is detected. And the result determines the connection between each SCSI recorder and the interface to the previous SCSI bus. That is, the state is detected by the SCSI bus detection function, and the connection state of the SCSI bus is switched according to the state and a preset address. By doing so, the access speed to the recording medium of the SCSI device is improved.

[0009]

Embodiments will be described below with reference to the drawings. The present invention can be used without changing the OS of the host system.
Also, without using a device with a special SCSI function (disconnect, reconnect, command cache function, etc.) and without complicated control, you can use multiple SCSI devices with the same general recorded contents. Access can be speeded up. This device has switching means for switching the connection to each SCSI device according to the status of the SCSI bus and the address information given in advance.

For example, when two devices, SCSI devices A and B, are connected, there is a means for connecting the SCSI bus and the devices A and B as follows. (1) Connect the devices A and B in a connection state in which signal lines are processed (connection state). (2) Connect device A in the normal SCSI bus state, device B
Is disconnected (connected state). (3) Connect device B in a normal SCSI bus state, device A
Is disconnected (connected state). As a function of the connection circuit, when the device is connected, it has a function of connecting the device in a disconnected state.

Further, in order to set one of the connection states 1 to 3 depending on the state of the SCSI bus, the following S
It has the detection functions ac of the CSI bus. a. SCSI reset detection function. b. Command phase detection function and CDB (Comm
and Descriptor Block) a function to detect a read command in the first byte, detect an address in the second byte and later of the CDB, and compare it with address data to detect an address <= set address. c. Command phase detection function and the first byte of CDB was not a read command, or CDB
The function to detect address> set address by detecting the address at the 2nd byte and comparing with the address data.

Further, due to the detection functions of a, b and c,
It has the function of switching the connection state of the bus to. Further, it has means for inputting a switching address for switching the connection state to or in the case of the states of b and c.

FIG. 1 is a block diagram for explaining an embodiment of a bus connection control device according to the present invention, in which 1 is an SCS.
I bus I / F (interface), 2 and 3 are device I / Fs
(Interface), 4 is an address switch, 5a, 5
Reference numeral b is a bus connection circuit, 6a and 6b are bus connection circuits, 7 is a bus conversion connection circuit, and 8 is a bus connection control circuit.

In this embodiment, the SCSI device is a CD-RO.
It is an M device, and there are two units, A and B. A medium having the same recorded contents is inserted into each device, and the logical block address to which the devices A and B are distributed has, for example, a block number of about 270,000 (41EB0 = 16) in the CD-ROM.
The number of blocks is 20,000
(Hexadecimal) Block. This address is specified by the CDB (Command Descriptor Block) 2 described later.
This address is used because it is only necessary to check up to the byte. In other words, it suffices to judge by looking at the value of the fifth digit.

The SCSI bus I / F1 is connected to the SCSI bus. The signal lines of the SCSI bus are RESET which is a reset signal and other control signals which are BSY (busy), SEL (selection), C / D (control data) and I / O.
(Input / output), MSG (message), REQ (request),
It is composed of ATN (attention), ACK (response), DB (data bit) 0-7 which is a data bus signal and DBP of the parity signal. Connected to the bus here is a host SCSI device that issues commands to the CD-ROM device. The devices I / F 2 and 3 are connected to the devices A and B, respectively. The ID numbers of the devices A and B are 0 and 1, respectively.

As an initial setting of this apparatus, first, the address switch 4 is set to an appropriate value (in the case of this embodiment, 2000).
0H) Set. The initial connection state of the SCSI bus is as follows. Signals from the SCSI bus are device A
Is connected to the device I / F 2 through bus connection circuits 5a and 7. Similarly, the device B is also daisy-chained to the device B through the bus connection circuits 6a and 7. The signals of the bus connection circuits 5b and 6b are specific to the SCSI bus (BS
Y, C / D, REQ, ACK, DBO) control signals.

The bus conversion connection circuit 7 receives the same signals from the devices A and B as inputs and converts them. The signals of the bus connection circuits 5a and 6a are other signals. Bus conversion connection circuits are devices A and B
BSY, C / D, and REQ of each of the signals are output to the SCSI bus, and A from the SCSI bus is output.
The CK signal is appropriately output to each device according to the state of the disconnected device, and the data bus 0 is output to the device B.
Signal is also output to the data bus 1. ACK
The control of is determined depending on the disconnection condition, such as disconnection at the detection of the 1st byte of the CDB and disconnection at the 2nd byte of the CDB. Therefore, determine which state to connect when connecting. To do.

The signals MSG, C / D, and I / O indicate that there is a phase between the initiator and the target, and the communication sequence is advanced by the 8-phase state transition. What is an initiator?
A device that acquires the right to use the bus and can select a target to communicate with from multiple devices connected to the bus. Generally, the initiator is the host computer, and in the case of SCSI, the controller can also be the initiator. .

FIG. 2 is a flow chart for explaining the operation of the bus connection circuit according to the state of the SCSI bus. Hereinafter, each step will be described in order. SCSI
When the bus state is the initial state or SCSI reset, only the bus connecting circuits 5a, 6a, 7 are connected (step 1), and then the command phase is judged (step 1).
2) It is judged whether the command in the command phase is a read command and address> setting address (step 3). If not address> setting address, only the bus connecting circuits 5a and 5b are connected (step 4), If the address> the set address, only the bus connection circuits 6a and 6b are connected (step 5). SCSI bus reset is SC
It can be known by the reset signal of the SI bus, and the command phase is a signal of C / D, I / O, MSG, and it can be known whether or not it is a read command. The address is S
It can be confirmed by the CSI data bus signal. C
The structure of DB is shown in Table 1 below.

[0020]

[Table 1]

FIG. 3 is a diagram showing a timing chart. In this embodiment, first, the address 0 is issued by the read command.
An example is shown in which −20000 (H) is specified, device A is selected, the next command specifies addresses 20001 (H) or higher, and device B is selected. The initial state of the bus connection is the connection state 1. When the selection phase for ID0 is executed, since the signal of the SCSI data bus 0 is connected to the data bus 1 of the device B (timing shown in a), the devices A and B are simultaneously selected. In addition, B for responding to the selection
C / indicating that the SY signal or command phase has been entered
Since the logical product of the D signal and the REQ signal indicating that the data transfer is ready is sent to the SCSI bus, the phases of the devices A and B or the data transfer proceed synchronously.

The bus connection control circuit includes C / D, I / O and M
Confirm that the command phase has been entered from the SG signal,
The data bus at the time when the ACK shown at the timing b is asserted is read to check whether it is a read command. Read command is usually 08H or 28H
However, in the present invention, 08H is checked. Each bit of the data bus is examined to determine if it matches 08H. If it is not a read command, the connection state is established.
If it is a read command, AC is applied to each device.
Try to return K.

Next, the SCSI data bus at the time when the second ACK is asserted and the address previously set by the address switch are checked. Since the address of the SCSI data bus was smaller than the set data bus, the connection state is set. In the connected state, the bus of the device A is directly connected to the SCSI bus, and therefore the subsequent series of phases is executed only for the device A.
When the command phase is entered again, the command is checked at the timing shown in c. If the command was a read command as in the previous time, the disconnected device is the CDB 1
It is determined whether it is disconnected at the second byte or the second byte, and if it was disconnected at the first byte last time, it is connected here and ACK is returned to both devices.
In the case of this embodiment, nothing is done.

The data bus is checked at the timing when the next ACK is asserted. In this case, since the address indicated by the data bus exceeds the set address, the device A is disconnected from the bus, the device B is connected in the previously disconnected state, and the device B is processed thereafter. . Since the connection of the device B at this time is in the same phase as when it was disconnected last time, it is processed without any problem. Also, if there is a SCSI reset in the middle phase, there is no problem because it starts from the beginning in the connected state.

[0025]

As is apparent from the above description, according to the present invention, it is possible to shorten the seek time of the device by connecting a plurality of devices having the same recorded contents without the intervention of the host. According to this method, the seek time can be shortened by increasing the number of connected devices. Further, by expanding the function and allocating an address assigned to each device to an area dedicated to the FAT and the other to a meaningful address such as a data area in a logical format, effective seek allocation can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a bus connection control device according to the present invention.

FIG. 2 is a flow chart for explaining the operation of the bus connection circuit according to the state of the SCSI bus in the present invention.

FIG. 3 is a diagram showing a timing chart in the present invention.

[Explanation of symbols]

1 ... SCSI bus I / F (interface), 2, 3 ...
Device I / F (interface), 4 ... Address switch, 5a, 5b ... Bus connection circuit, 6a, 6b ... Bus connection circuit, 7 ... Bus conversion connection circuit, 8 ... Bus connection control circuit.

Claims (1)

[Claims] 1. A bus connection controller used in a SCSI system including at least one initiator for commanding a command, and a plurality of targets for receiving a command from the initiator, wherein the bus connection control device is interposed between the initiator and the target. In addition, the bus connection control device is provided with a switching means capable of changing the connection of the signal terminal on the target side based on the information in the SCSI phase from the initiator and the address information given in advance.