JPH0519919A - Host system expansion device - Google Patents

Abstract

(57) [Abstract] [Purpose] When expanding the system by daisy chain connection, reduce the mistakes and troubles when connecting and disconnecting the terminating device, and ensure the operation of the device. [Structure] The optical sensor 7 is composed of an LED 10 and a Cds 11, and when the connector 8 is inserted, the LED 1
Light from 0 is blocked. That is, when the connector 8 is connected and the light to the Cds 11 of the optical sensor 7 is blocked, C
The resistance of ds11 increases, a current is supplied to the base of the transistor unit 13 to turn on the relay 12, while the relay 12 is turned off when the connector 8 is not connected. As a result, the termination circuit is automatically switched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a host system expansion device, and more particularly to a daisy chain.
The present invention relates to a host system expansion device that expands a peripheral device by connection or an input bus line according to the SCSI bus standard.

[0002]

2. Description of the Related Art Personal computers, word processors, DTP (desk top publishing), C
2. Description of the Related Art With the spread of electronic devices such as AD (Computer-Aided Design), it is widely practiced to expand the system by adding peripheral devices such as magnetic disks and magnetic tapes to a host system using them.

When expanding the system in this way, there is a method of connecting peripheral devices by daisy chain connection to add peripheral devices. This daisy chain connection connects from one connection port of the control device to the input side connection port of the peripheral device to be controlled, and further from the output side connection port of the peripheral device to the input side of the next peripheral device. This is the connection method that will be used. Then, the output side of the termination device corresponding to the final connection is short-circuited by turning on the built-in termination circuit. on the other hand,
The termination circuit built in the peripheral device which is not connected to the termination circuit and is in the middle of connection is turned off.

On the other hand, it is possible to arbitrarily mix initiator devices (devices that serve as hosts) and target devices (devices that are accessed by the host) on a bus line that connects various devices and connect up to eight devices. There is a SCSI standard for buses (ANSI X3.131-1986). FIG. 9 shows an example of the connection state of each device according to the SCSI standard. As shown in FIG. 9, the three initiator devices 2 are provided on the SCSI bus 21.
When 2, 23, 24 are connected, the system is expanded by connecting five target devices 25, 26, 27, 28, 29.

[0005]

When a host system such as a word processor, a personal computer, a DTP (desk top publishing) and a peripheral device such as a magnetic disk and a magnetic tape are connected in a daisy chain, when there are a plurality of peripheral devices. The termination circuit in the peripheral device other than the termination has to be turned off by manually operating the DIP switch or the like. In addition, when the peripheral device is disconnected, the terminal circuit of the peripheral device that is newly terminated also needs to be manually turned on in the same manner. Therefore, it takes time and effort to operate the switch. Also, due to an operation error
If the termination is connected when it is not needed, or vice versa, the impedance matching with the cable may be reduced, which may adversely affect the operation of the device.

On the other hand, in the connection of a general SCSI device,
As shown in FIG. 9, the initiator device and the target device can be mixed and connected up to eight. However, more than seven target devices cannot be connected to one initiator device, and if there are two or more initiator devices, only a smaller number of target devices can be connected. There wasn't. That is, in the conventional expansion of the host system using the bus based on the SCSI standard, the number of expandable targets has a certain limit.

Therefore, a first object of the present invention is to reduce mistakes and troubles at the time of connecting and disconnecting a terminating device when the system is expanded by a daisy chain connection, and ensure the operation of the device. To provide a host system expansion device. A second object of the present invention is SCS.
An object of the present invention is to provide a host system expansion device capable of connecting eight or more initiator devices and target devices when system expansion is performed by a network conforming to the I standard.

[0008]

According to a first aspect of the present invention, a host system or an input-side connector daisy-chained to a peripheral expansion device daisy-chained with the host system and another peripheral expansion device are daisy-chained. An output side connector to be connected, a connection detecting means for detecting that another peripheral expansion device is connected to the output side connector, and a termination signal for short-circuiting the termination of the daisy chain connection by a detection signal from the connection detecting means. The short-circuit means is provided in the host system expansion device to achieve the first object. According to the second aspect of the invention, a SCSI initiator bus to which N initiator devices are connected and M (M
+ N ≦ 7) a SCSI target bus to which a plurality of SCSI target buses connected to the target device are connected, and the SCSI initiator bus to the SCSI target bus of the corresponding channel according to a channel request signal supplied from the initiator device. The second object is achieved by providing the host system expansion device with bus connecting means for connection.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a host system expansion device of the present invention will be described in detail below with reference to FIGS. First Invention In the first invention, a host system expansion device will be described by taking an additional HDD used in a daisy chain connection as an example. FIG. 1 shows a system configuration of an embodiment of the first invention. As shown in FIG. 1, the word processor 1, which is the host device, includes the first and second additional HDDs 2, 3
It is assumed that the system is expanded from the second. That is, the output side (OUT) of the word processor 1 and the input side (IN) of the first additional HDD are also connected to the first additional H
The output side of the DD2 and the input side of the second additional HDD are daisy chain connected.

FIG. 2 shows the first and second additional HDs.
3 shows the internal configuration of D. As shown in FIG. 2, the additional HDD has an input side connector 4 and an output side connector 5 connected by a bus 6. An optical sensor 7 is incorporated in the output side connector 5, and it is configured to detect that the connector 8 has been inserted and notify the termination switching device 9 of it.

FIG. 3 shows a circuit configuration of the terminal switching device 9 and the optical sensor 7. The optical sensor 7 is composed of an LED (light emitting diode) 10 and a Cds (cadmium sulfide) 11, and when the connector 8 is inserted, the LED
The light from 10 is blocked. The terminal switching device 9 also includes a relay 12 and a Darlington-connected transistor unit 13 that turns the relay 12 on and off according to a signal supplied from the optical sensor 7. That is, the connector 8 is connected and the Cds 11 of the optical sensor 7 is connected.
When the light to the relay is cut off, the resistance of Cds11 increases, and the current is supplied to the base of the transistor unit 13 so that the relay 1
2 is turned on, while the relay 12 is turned off when the connector 8 is not connected.

The on / off operation of the termination circuit by the additional HDD thus configured will be described. For example, the first
When only one additional HDD 2 is connected to the output side connector 5, nothing is connected to the output side connector 5, so that the relay of the terminal switching device 9 is turned on and the terminal of the bus is terminated. On the other hand, if another second additional HDD 3 is connected as shown in FIG.
Since the cable 8 is connected to the output side connector 5 of 2, the relay of the termination switching device 9 of the first additional HDD 2 is turned off and the termination circuit is disconnected. Second additional HDD
No. 3 is connected to the output side connector, so the termination circuit is turned on and terminated.

Next, a second embodiment of the first invention will be described. In the second embodiment, in order to switch the termination circuit, when the connector has two or more empty pins (NC), the empty pin is used to detect the termination. There is. FIG. 4 shows a state in which the additional HDD according to the second embodiment is connected. As shown in this figure, two empty pins of the input side connector 4 of the second additional HDD 3 are short-circuited by the connection P. On the other hand, 2 of the output side connector 5 of the first additional HDD 2 corresponding to the vacant pin of the shorted second additional HDD 3
A voltage detection circuit 1 that applies a voltage (for example, +5 V) to one of the two empty pins and detects the voltage to the other empty pin
4 is connected. The voltage detection circuit 14 is connected to the termination switching circuit 9.

FIG. 5 shows a circuit configuration of the voltage detection circuit 14 and the termination switching device 9. As shown in this figure, the voltage of 5V applied from one empty pin of the first additional HDD 2 is applied to the connection cable and the second additional HDD.
When detected by the voltage detection circuit 14 via the input side connector 4 of 3 and the connection P, the transistor unit 1 of the termination switching device 9 is detected.
3 is turned on and the relay 12 is turned off.

Therefore, for example, when only the first additional HDD 2 is connected to the host device, nothing is connected to the output side connector 5, so the voltage detection circuit 1
No voltage is detected at 4 and the termination circuit 9 is on. On the other hand, when the second expansion HDD 3 is connected, the output side connector 5 of the first expansion HDD 2 and the second expansion HD
A cable is connected to the input side connector of D3. Therefore, the voltage returns to the output side of the first additional HDD 2 through the input side connector 4 of the second additional HDD 3, so the voltage detection circuit 14 of the first additional HDD 2 detects this voltage and terminates it. The relay 12 of the switching device 9 is turned off. Further, when the second additional HDD 3 is disconnected, the termination circuit of the first HDD 2 is turned on in the reverse order.

As described above, the first and second
According to the embodiment of the present invention, in the peripheral device, the terminating circuit is automatically turned off by inserting the connector, and the terminating circuit is automatically turned on by disconnecting the connector. There is no need to operate, and operability is improved. Further, in the case of manual operation, the operation of the switch may be mistaken, so that the terminal may not be properly switched and the device may not operate normally, but in the present invention, the terminal is automatically and surely switched. Therefore, the reliability of operation is increased.

Second Invention In the second invention, the host system expansion device will be described as an example of a SCSI bus switching device used for a SCSI standard bus. FIG. 6 shows a state in which the system is expanded using the SCSI bus switching device as a target device. In FIG. 6, since three initiators are connected as an example, the SCSI bus switching device is used as one target device, and the SCSI buses to which four target devices are connected are connected for three channels. There is. The number of channels of the SCSI bus can be further increased or decreased depending on the setting of the command of the SCSI bus switching device. Channel switching is performed by supplying one command to the SCSI switching device.

FIG. 7 shows the configuration of such a SCSI bus switching device. SCSI bus switching device is S
A CSI controller 31 is provided. The SCSI controller 31 is an interface circuit with the SCSI initiator bus 36, and is controlled by the controller 32. The control device 32 is a part that controls the bus switching control operation.
Input / output of commands and data with the initiator device via the I controller 31 and SCSI bus selector 33
Control. The memory 34 is a ROM that stores various control programs such as bus switching control by the control device 32.
(Read-only memory) and RAM (random access memory) as a data buffer of the SCSI bus controller 31 and a work memory of the control block 32
Consists of.

The SCSI bus selector 33 receives a control signal 37 from the control device 32 in accordance with a channel switching request command from the initiator device, and selects one of the desired channels (Ch1, Ch2, ..., ChX) of the SCSI target bus 35. It is connected to the SCSI initiator bus 36.

The operation of inputting / outputting data or the like between the initiators in the SCSI bus switching device thus configured will be described with reference to FIG. When an initiator device supplies a command requesting the channel number of the currently connected SCSI target bus, the SCS
The I-bus switching device responds with data of the currently connected channel number. If the responding channel number is different from the desired channel, the initiator device requests switching to the desired channel, and accordingly, the SCSI device.
The bus switching device switches the connection to the desired channel. Then, the initiator device transfers status data corresponding to the switching to the initiator device. The initiator device outputs a predetermined command to a predetermined target device connected to the connected SCSI target bus 35.

As described above, in this embodiment, by connecting the bus switching device as a target device on the SCSI bus, it is possible to expand to a larger network without changing other SCSI devices. Is possible. Also, for the program on the initiator device side, the bus is switched for each channel and used, so that control and management are easy, and changes due to system expansion are reduced.

[0022]

According to the first aspect of the present invention, the connection detecting means detects that another peripheral expansion device is connected to the output side connector, and the detection signal detects the termination of the daisy-chain connection. Since the circuit is short-circuited, when the system is expanded by the daisy chain connection, mistakes and troubles at the time of connecting and disconnecting the terminal device can be reduced and the operation of the device can be ensured. According to the invention described in claim 2, since the bus connecting means for connecting one of the SCSI target buses of a plurality of channels to the SCSI initiator bus to which 7-N or less target devices are connected is provided, the SCSI standard is provided. When the system is expanded by the network according to the above, it is possible to connect eight or more initiator devices and target devices.

[Brief description of drawings]

FIG. 1 is a system configuration diagram in which an additional HDD according to an embodiment of the first invention is connected.

FIG. 2 is an internal configuration diagram of the additional HDD of the above.

FIG. 3 is a circuit diagram of an end switching device and an optical sensor of the above.

FIG. 4 is an explanatory diagram showing a connection state of an additional HDD according to another embodiment of the first invention.

FIG. 5 is a circuit diagram of a voltage detection circuit and an end switching device of the additional HDD of the above.

FIG. 6 is a system configuration diagram of an embodiment of the second invention.

FIG. 7 is a configuration diagram of a SCSI bus switching device of the above.

FIG. 8 is an explanatory diagram of an input / output operation of data or the like between the initiators in the SCSI bus switching device.

FIG. 9 is an explanatory diagram showing a state in which each device is connected according to the conventional SCSI standard.

[Explanation of symbols]

A few extra HDDs 4 Input side connector 5 Output side connector 7 Optical sensor 9 Terminal switching device 12 relays 14 Voltage detection circuit 31 SCSI bus controller 32 control device 33 SCSI Bus Selector 36 SCSI Initiator Bus 35 SCSI target bus

Claims (2)

[Claims] 1. An input side connector which is daisy chain connected to a host system or a peripheral expansion device daisy chain connected to the host system, an output side connector which is daisy chain connected to another peripheral expansion device, and this output side connector. A peripheral, which is provided with connection detecting means for detecting that another peripheral expansion device is connected to the terminal, and terminal short-circuiting means for short-circuiting the terminal of the daisy chain connection by a detection signal from the connection detecting means. Host system expansion device as an expansion device. 2. An S connected to N initiator devices.
SC with CSI initiator bus and M (M + N ≦ 7) target devices connected
SCSI in which multiple channels of SI target bus are connected
A host system expansion device comprising: a target bus; and a bus connecting means for connecting the SCSI initiator bus to a SCSI target bus of a corresponding channel in accordance with a channel request signal supplied from an initiator device.