JPH0877079A - External storage device - Google Patents

Abstract

PURPOSE: To prevent data destruction and system abnormality by making a power-OFF indication ineffective until writing to a storage medium ends if a command which is issued right before is a write command although the power- OFF indication is made. CONSTITUTION: The main body device 1 of a host device and the external storage device 10 are connected with an interface signal E and AC electric power A is supplied. When a command decision circuit 11 decides that the interface signal E is the write command, a power-OFF control circuit 12 is informed of that and generates and outputs a stand-by indication C for making the power-OFF indication ineffective for a certain time to a power source control part 13 in response to the information. Therefore, even if there is a supply cutoff indication for the AC power source A from the main body device 1 or a power-OFF indication B made by an operator, the power source control part 13 does not disconnect a DC power source F while the stand-by indication C is present and disconnects the output of the DC power source F once the stand-by indication C is ceased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external storage device, and more particularly to an external storage device which stores write data in a buffer such as a temporary write cache in response to a write command from the information processing device and then stores the write data in a storage medium. The present invention relates to an external storage device configured to actually perform writing.

[0002]

2. Description of the Related Art As an example of a control method of operating power supply in a conventional external storage device of this type, generally, a main body device in which an input power supply of the external storage device is a host device via a power on / off switch of the external storage device. It is often supplied from a service outlet such as
The power supply of the external storage device is directly controlled by turning on / off the power of the main body device. Therefore, if the operator mistakenly turns off the power supply of the main unit during the writing operation of the external storage device, there is a problem that a system abnormality occurs due to data destruction and a storage medium is damaged.

Therefore, in Japanese Unexamined Patent Publication No. 4-162115 and Japanese Unexamined Patent Publication No. 4-114218, it is detected that the external storage device is in the writing operation by an interface signal between the main body device and the external storage device. A method has been proposed in which the power supply is cut off after the write operation is completed.

[0004]

In the external storage device having the write cache function, which is becoming the mainstream at present, the write data from the main body device is temporarily taken into the write cache buffer, and thereafter the storage medium is transferred from the write cache buffer. The operation of actually writing the write data to is performed.

In the external storage device having such a write cache function, the interface signal is brought into a state indicating the end of writing when the write data is taken into the write cache buffer for data transfer. In the technique of the publication, there is still a risk that the power is cut off before actually writing data from the write cache buffer to the storage medium or at the start of writing. Therefore, the problem similar to the normal power control method still remains. Will occur.

Therefore, the present invention has been made in order to solve the drawbacks of the prior art, and its purpose is to cause data destruction, system abnormality, etc. even when the write cache function is provided. An object of the present invention is to provide an external storage device capable of power-off control that does not occur.

[0007]

An external storage device according to the present invention comprises a storage medium, a buffer means for temporarily storing write data in response to a write command to the storage medium from a host device, and a buffer device from the host device. In response to the write command, at least the power supply control means for invalidating the power-off instruction during the period until the writing of the write data from the buffer means to the storage medium is completed.

[0008]

When the write command is issued from the host device, even if there is a power-off instruction until the transfer of the write data from the external storage device buffer to the storage medium is completed, this is invalidated and the data is written to the storage medium. The power can be turned off after the actual termination.

[0009]

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

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, the main body device 1 which is a host device and the external storage device 10 are connected by an interface signal E, and an AC (alternating current) power supply A is supplied from the main body device 1 to the external storage device 10.

The external storage device 10 stores the data in the storage section 16, the command determination circuit 11 for determining a write command by the interface signal E, and disables the power-off for a certain time in response to the determination result. And a power supply control unit 13 that controls the supply of the DC power supply F in response to the power supply cutoff standby signal C, the AC power supply A, and the power supply on / off instruction B.

The storage unit 16 includes an interface control unit 17 that forms an interface with the interface signal E, a buffer 18 that temporarily stores write data, and a storage medium 19.

If the command determination circuit 11 determines that the interface signal E is a write command, the power-off control circuit 12 is notified of that fact. In response to this notification, the power-off control circuit 12 generates a standby instruction C for invalidating the power-off instruction for a certain period of time to generate the power-supply control unit 1.
Output to 3.

Therefore, even if the AC power supply A is cut off from the main unit 1 or the operator turns off the power B,
While the standby instruction C is present, the power control unit 13 sets D
The output of the C (DC) power supply F is continued without being cut off, and the output of the DC power supply F is cut off only when the standby instruction C disappears.

The generation period of the standby instruction C is at least from the time when the write command is detected until the data writing from the buffer 18 to the storage medium 19 is completed, and this period is determined by the specifications of the storage unit 16. A timer or the like should be used according to the specifications.

FIG. 2 is a block diagram showing an example of the power supply controller 13. The DC output determination circuit 20 receives the disconnection standby instruction C, the power supply on / off instruction B, and the AC supply A from the main body apparatus 1 from the power supply disconnection control circuit 12 as inputs, and determines the combination of the logical states of these inputs A to C. Accordingly, the DC output permission D is generated.

The AC / DC conversion circuit 21 receives the AC supply A from the main unit 1 and generates a DC power supply.
The battery 22 is a battery for backing up the storage medium 19. This battery output serves as an operating power source for the DC determination circuit 20 and also serves as an input to the DC output circuit 23.

It is assumed that the DC output of the AC / DC conversion circuit 21 is also applied to the DC output circuit 23 and is logically an OR input. The DC output circuit 23 selectively derives the battery output or the output of the AC / DC conversion circuit 21 according to the DC output permission signal D from the DC output determination circuit 20 and uses it as the operating power supply of the storage unit 16. is there.

It is assumed that the state of the one output D with respect to the three inputs A to C of the DC output determination circuit 20 has the relationship shown in FIG. Therefore, while the disconnection standby instruction signal C is “present” and active, even if the AC supply is cut off or there is a power-off instruction, all are invalidated and the DC output is for a period determined by the above timer. That is, the power of the storage unit 16 is not turned off.

An example of a logic circuit for realizing the input / output logic (FIG. 3) of the DC output determination circuit 20 shown in FIG. 2 is shown in FIG. 4, and the input / output signal definition is shown in FIG. In FIG. 4, 51 to 52 are 2-input AND gates, and 53 is a 2-input OR gate.

[0021]

As described above, according to the present invention, even if there is a power-off instruction from the operator or the AC supply is stopped from the host device, if the command issued immediately before is a write command, at least from the buffer. These instructions are invalidated and power supply is continued until the data is written to the storage medium and is ended, so that there is no problem such as data destruction or system abnormality.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of a power supply control unit 13 in the block of FIG.

3 is a diagram showing an input / output logic state of a DC output determination circuit 20 of the block of FIG.

FIG. 4 is a circuit diagram showing an example of a DC output determination circuit 20 of FIG.

5 is a diagram showing definitions of input / output signals of the circuit of FIG.

[Explanation of symbols]

 1 Main Unit 10 External Storage Device 11 Command Judgment Circuit 12 Power Supply Disconnection Control Circuit 13 Power Supply Control Unit 16 Storage Device 17 Interface Control Unit 18 Buffer 19 Storage Medium

Claims (3)

[Claims] 1. A storage medium, buffer means for temporarily storing write data in response to a write command from the host device to the storage medium, and at least from the buffer means in response to a write command from the host device. And a power supply control means for invalidating the power-off instruction during the period until the writing of the write data in the storage medium is completed. 2. The power supply control means includes a command determination means for determining the write command and an invalidation signal generation means for generating an invalidation signal for invalidating the period power-off instruction in response to the determination. The external storage device according to claim 1, further comprising: 3. The backup power supply for backing up the storage medium when the storage medium is powered off,
It has a power supply circuit for receiving an AC power supply from the host device and generating an operation DC output of the external storage device, and means for selectively deriving each DC output of the power supply circuit and the backup power supply. 2. The external storage device according to claim 1, wherein the external storage device is configured to derive the DC output of the backup power supply in response to the generation of the invalidation signal when the supply of the AC power supply from the host device is stopped.