JP2003195993A - Scsi device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an SCSI device capable of supplying a power source of proper term power when connected to an external SCSI device, capable of reducing electric power consumption, and capable of realizing these with the simple constitution. <P>SOLUTION: This SCSI device has a terminator 1 and an internal power source 2, and has a voltage comparing part 4 for comparing a term power voltage value of the power source supplied to the terminator 1 from an external part with a reference voltage value generated by dividing voltage of the internal power source 2, and a changeover switch 5 for switching power source supply to the terminator 1 from the internal power source 2 to an ON state when the term power voltage value is less than the reference voltage value, and the power supply source to the terminator 1 from the internal power source 2 to an OFF state when the term power voltage is not less than the reference voltage value as a comparing result by the voltage comparing part 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to SCSI (Small C
S having an omputer system interface)
Concerning CSI devices (for example, peripheral devices such as personal computers and printer devices, scanner devices, magnetic disk devices, optical disk devices, etc.), especially when connecting to an external SCSI device, a suitable TERM POWER power source is supplied to reduce power consumption. And an SCSI device capable of stabilizing the SCSI bus.

[0002]

2. Description of the Related Art Generally, SCSI devices used for personal computers and peripheral devices are connected to each other in a daisy chain manner by a common cable (SCSI bus). SCSI bus has 8 data lines and 1
Data parity lines and 9 control lines (the above total 9 data lines and 9 control lines are called general signal lines), and term power (termination resistor circuit). Power supply line) and a ground line.

Now, a system configuration of a conventional host computer using a SCSI device and peripheral devices, that is, a so-called SCSI system configuration will be described. A terminator, which is a terminating resistance circuit, is connected to both ends of the SCSI system composed of a plurality of SCSI devices.

FIG. 3 shows a conventionally used SCSI.
It is a block diagram which shows an example about the structure of a system. In FIG. 3, 11 is a SCSI device (for example, a host computer), 12 to n are SCSI devices (peripheral devices), 11a, 12a, na are driver circuits, 11b,
12b and nb are receiver circuits, 11c, 12c and nc are SCSI connectors, 13 is a SCSI cable, 14 and 1
5 is a terminator.

As shown in FIG. 3, terminators 14 and 15 which are terminating resistor circuits are connected to devices located at both ends of the SCSI system, a SCSI device (for example, a host computer) 11 and a SCSI device n, respectively.
The SCSI devices 11, 12, and n are connected to each other by a SCSI cable 13.

The terminator power is supplied to the terminators 14 and 15. As a power supply method, a method of using an internal power supply of a SCSI device such as an HDD or S
There is a method of receiving power supply from a term power line (terminator power line) included in the CSI bus. Power is supplied to the term power line from an internal power supply such as a host computer.

Since there are two types of power supply methods for terminators as described above, one method is preset in a SCSI device such as a conventional HDD,
Some of them are provided with switching means so that either method can be selected.

For example, Japanese Laid-Open Patent Publication No. 10-187310 has a power supply switching switch for switching between the means for using the power supply of the term power line and the means for using the internal power supply as the power supply system for the terminator. SCS
An I device (hereinafter referred to as a conventional example) is disclosed. The power supply switching switch is an internal power supply switch for switching whether to supply power from the internal power supply to the terminator under the control of the power supply monitoring circuit.

According to this conventional example, it is possible to switch from the system utilizing the power supply of the term power line to the system utilizing the internal power source by using the power source switching switch. Therefore, even if the SCSI device connected to the system is premised on the power supply of the term power line, when the power supply of the term power line is stopped, switching to the method of using the internal power supply enables the connection of the SCSI device. The configuration can be normal.

[0010]

However, the specific circuit configuration of the power supply monitoring circuit, the power supply switching means, etc. is not described in the conventional example. Further, the means for automatically switching the power source is not specifically described.

The present invention provides an SCSI device which can supply an appropriate power of term power when connected to an external SCSI device, reduce power consumption, and can realize these with a simple configuration. The purpose is to provide.

[0012]

The SCSI device of the present invention is a SCSI device having a terminator and an internal power supply, and divides the term power voltage value of the power supply externally supplied to the terminator and the voltage of the internal power supply. When the term power voltage value is less than the reference voltage value as a result of the comparison by the comparing means for comparing with the reference voltage value generated by the comparison means, the power supply from the internal power supply to the terminator is turned on. In addition, when the term power voltage value is equal to or higher than the reference voltage value, it has a switching means for switching the power supply from the internal power source to the terminator to an OFF state.

The reference voltage value may be generated by a voltage dividing resistor connected in series with an internal power supply.

The switching means is arranged between the internal power source and the terminator and is turned on by a signal from the comparison means.
It may be a transistor that is turned on / off.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a SCSI device according to an embodiment of the present invention.

As shown in FIG. 1, the SCSI device according to the embodiment of the present invention comprises a terminator 1 (termination resistance circuit).
The internal power supply 2, the term power voltage value of the power supply supplied from the external SCSI device 3 to the terminator 1 through the term power line L1, and the reference voltage value generated by dividing the internal power supply 2. Voltage comparison unit 4 for comparison
As a result of comparison by the voltage comparison unit 4, when the term power voltage value is less than the reference voltage value, the power supply from the internal power supply 2 to the terminator 1 is turned on and the term power voltage value is equal to or higher than the reference voltage value. If there is, it has a changeover switch 5 for switching the power supply from the internal power supply 2 to the terminator 1 to the OFF state.

The terminator 1 is composed of two resistors R1 (for example, a 220Ω resistor) and R2 (for example a 330Ω resistor) connected in series.
The terminals T1 to T3 are connected. T1 is a contact with the term power line L1, T2 is a contact with the signal line L2, and T3 is a terminal with the ground line L3. A driver circuit and a receiver circuit (D / R circuit) 6 are connected to the terminal T2.

Then, as shown in FIG. 3, by using the SCSI devices 11, 12, and n, it is possible to construct a SCSI system consisting of one host computer and up to seven peripheral devices. it can.

The reference voltage value is generated by a plurality (two in the example of FIG. 1) of voltage dividing resistors R3 and R4 connected in series between the internal power supply 2 and the ground.

The changeover switch 5 is a transistor which is arranged between the internal power supply 2 and the terminator 1 and which is turned on / off by a signal from the voltage comparison section 4. The transistor is, for example, a PNP transistor, the emitter is connected to the internal power supply 2, and the collector is a terminal T1
The terminator 1 is connected via a resistor R5, and the voltage comparator 4 is connected to the base via a resistor R5. Reference numeral 7 is a SCSI connector.

FIG. 2 shows a SCSI according to the embodiment of the present invention.
6 is a flowchart for explaining the operation of the device.

First, power is supplied to the terminator 1 from the external SCSI device 3 through the term power line L1 (step S1). Further, the voltage of the internal power source 2 is divided by the voltage dividing resistors R3 and R4 to generate a reference voltage (step S2).

Next, the voltage comparison unit 4 uses the external SCSI.
Terminator 1 from device 3 via term power line L1
The term power voltage value of the power source supplied to the power supply circuit is compared with the generated reference voltage value (step S3). As a result of comparison by the voltage comparison unit 4, when the term power voltage value is less than the reference voltage value, the changeover switch 5 is turned on (step S4), and power is supplied from the internal power supply 2 to the terminator 1 (step S4). S5).

When the term power voltage value is equal to or higher than the reference voltage value, the changeover switch 5 remains in the OFF state (step S6), power is not supplied from the internal power source 2 to the terminator 1, and the external SCSI device 3 is used. Power is supplied to the terminator 1 through the term power line L1 (step S1).

According to the embodiment of the present invention, when the term power voltage value is equal to or higher than the reference voltage value, power is not supplied from the internal power supply 2 of the self device, so that unnecessary power consumption can be prevented and the power consumption can be reduced. Electricity can be saved.

When the term power voltage value is less than the reference voltage value, the external SCSI device 3 connects the term power line L.
It is predicted that power is not supplied via 1 or the term power voltage value has dropped due to some abnormality, but since power is supplied from the internal power supply 2 of the self device, the SCSI bus is stabilized. be able to.

Furthermore, since the reference voltage value is generated by dividing the voltage of the internal power supply 2, the structure can be simplified.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of technical matters described in the claims. For example, a variable resistor may be used as the voltage dividing resistor in order to set a desired reference voltage value.

[0029]

According to the embodiments of the present invention, when the term power voltage value is equal to or higher than the reference voltage value, power is not supplied from the internal power source of the self device, so that unnecessary power consumption can be prevented. It is possible to reduce power consumption.

If the term power voltage value is less than the reference voltage value, it is predicted that power is not supplied from the external SCSI device via the term power line, or that the term power voltage value has dropped due to some abnormality. However, since the power is supplied from the internal power supply of the self device, SCSI
It is possible to stabilize the bus.

Furthermore, since the reference voltage value is generated by dividing the voltage of the internal power supply, the structure can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a SCSI device according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining an operation of the SCSI device according to the exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing an example of the configuration of a conventionally used SCSI system.

[Explanation of symbols]

1: Terminator 2: Internal power supply 3: External SCSI device 4: Voltage comparison unit 5: Changeover switch 6: D / R circuit 7: SCSI connector L1: Term power line L2: signal line L3: Ground wire

Claims (3)

[Claims] 1. An SCS having a terminator and an internal power supply.
In the device I, a comparison means for comparing a term power voltage value of a power supply supplied from the outside to a terminator and a reference voltage value generated by dividing the voltage of the internal power supply, and a comparison result by the comparison means. When the term power voltage value is less than the reference voltage value, the power supply from the internal power supply to the terminator is turned on, and when the term power voltage value is the reference voltage value or more, the internal power supply to the terminator is changed. A switching device for switching the power supply to an OFF state, and a SCSI device. 2. The SCSI device according to claim 1, wherein the reference voltage value is generated by a voltage dividing resistor connected in series to an internal power supply. 3. The switching means is arranged between an internal power source and a terminator, and is turned on by a signal from the comparing means.
3. The SCSI device according to claim 1, wherein the SCSI device is a transistor that is turned on / off.