JP2740685B2 - Storage device backup circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backup circuit for a storage device (hereinafter, referred to as “memory”).

2. Description of the Related Art Conventionally, such a backup circuit supplies an auxiliary power supply voltage from an auxiliary power supply to hold data stored in a memory when the supply of the main power supply voltage from the main power supply to the memory is interrupted. The data stored in the memory can be used again when the voltage supply is restarted. FIG. 2 shows a specific configuration example of such a backup circuit. (1) is a main power supply terminal to which a main power supply voltage Vm is supplied from a main power supply of a system (for example, a central processing unit), and (2) is When a main power supply voltage Vm is supplied from a main power supply terminal (1), the main power supply voltage Vm is automatically closed and a memory selection circuit to be described later, a switch circuit for allowing supply of the main power supply voltage Vm to a memory and an auxiliary power supply,
(3) is a detection signal of a high level (hereinafter referred to as “H level”) by detecting the main power supply voltage Vm from the main power supply terminal (1).
The main power supply voltage detection circuit that outputs En, (4) is operable when the detection signal En supplied from the main power supply voltage detection circuit (3) becomes H level, and is supplied to the first signal input terminal (5). The memory selection circuit (4) performs a memory selection operation based on a memory selection signal CS1 from a system to be executed. When the memory selection circuit (4) described later is selected by the memory selection signal CS1, a low level (hereinafter referred to as “L level”) is selected. ) Is output, and when not selected, an H-level selection signal is output. In (6), when the selection signal CS2 supplied from the memory selection circuit (4) becomes L level, the memory is selected and data can be written or stored (ie, written) data can be read. The memory (6) is supplied to the data input / output terminal (8) when the read / write signal R / W from the system supplied to the second signal input terminal (7) in the selected state is at the L level. Write data from the system, read the stored data when the read / write signal R / W is at the H level, and read the data input / output terminal (8)
It is supplied to the system side more. And
When the selection signal CS2 supplied from the memory selection circuit (4) becomes H level, the memory (6) is in the non-selected state and the second memory (6) is in the second state.
A read / write signal R / W and data from the system supplied to the signal input terminal (7) and the data input / output terminal (8) are not accepted, and writing of data to the memory and reading of stored data are impossible. become. Writing and reading of data to and from the memory (6) can be performed when the power supply voltage supplied to the memory (6) is equal to or higher than the memory protection voltage Vd. Is held, but when the voltage is equal to or lower than the memory protection voltage Vd, the data stored in the memory (6) is not held. Therefore, for example, when the supply of the main power supply voltage Vm (> Vd) to the main power supply terminal (1) is cut off due to the turning off of the main power supply of the system, the main storage for storing the data stored in the memory (6) is performed. Power supply voltage Vm
An auxiliary power supply (9) for supplying an auxiliary power supply voltage Vs (Vm>Vs> Vd) is provided in place of the auxiliary power supply (9).
Is constituted by a chargeable capacitor, for example, and is charged by the main power supply voltage Vm when the main power supply voltage Vm is supplied. When the main power supply voltage Vm is cut off, discharge is started and the memory selection circuit (4) and the memory ( The auxiliary power supply voltage Vs is supplied to 6).

Therefore, the main power supply terminal (1) is connected to the main power supply voltage Vm from the main power supply.
Is supplied, the memory selection circuit (4) performs a memory selection operation based on the memory selection signal CS1 from the system, and reads / writes the read / write signal R / W from the system to the selected memory (6). , The data is written or the stored data is read. And the main power supply voltage to the main power supply terminal (1)
When the supply of Vm is cut off, the auxiliary power supply (9) in the charged state starts discharging and supplies the auxiliary power supply voltage Vs to the memory selection circuit (4) and the memory (6) instead of the main power supply voltage Vm. Will do. At this time, when the main power supply voltage Vm is not supplied from the main power supply terminal (1), the switch circuit (2) automatically opens to separate (cut off) the main power supply side and the auxiliary power supply (9) side. Therefore, the auxiliary power supply voltage Vs supplied from the auxiliary power supply (9) does not leak to the main power supply. At this time, since the detection of the interruption of the supply of the main power supply voltage Vm is detected and the detection signal En output from the main power supply voltage detection circuit (3) is at L level, the memory selection circuit (4) Is forced to the H level irrespective of the read / write signal R / W from the system, and the memory (6) is set to the non-selection state. Therefore, in the state of supply of the auxiliary power supply voltage Vs, writing and reading of data to and from the memory (6) become impossible,
The data stored in the memory (6) is retained (that is, backed up) as it is. When the supply of the main power supply voltage Vm to the main power supply terminal (1) is resumed in such a backup state, the restart of the supply is detected by the main power supply voltage detection circuit (3), and the switch circuit (2) ), The auxiliary power supply (9) is charged again, and the main power supply voltage Vm is supplied to the memory selection circuit (4) and the memory (6). Reading becomes possible.

However, in the backup circuit having such a conventional configuration, the auxiliary power supply (9) is formed of a capacitor and supplies the auxiliary power supply voltage Vs by discharging the auxiliary power supply, so that the power supply capability is limited. If power is supplied for a long period of time, the auxiliary power supply voltage Vs gradually decreases due to power consumption in the memory selection circuit (4) and the memory (6), and becomes lower than the memory protection voltage Vd. There was. For this reason, conventionally, check data (for example, “ABCD”) is written to the memory before the supply of the main power supply voltage Vm is cut off,
When the supply of the main power supply is resumed, first, the check data written in the memory (6) is read out and compared with the check data "ABCD" in the system, and when they match, the data stored in the memory (6) is retained, that is, backed up. It was determined that the backup was incomplete, and the stored data was used again.If the read check data was not "ABCD", the backup was determined to be incomplete and the stored data was not used. .

However, when determining whether or not backup data has been backed up by comparing check data, if the number of check data is small, the data may coincide with the check data by accident even though the backup data is not actually backed up. Had a problem with sex. On the other hand, when the number of check data is large, the memory is wasted wastefully, which causes a problem that the memory cannot be used effectively and that unnecessary time must be spent for processing the check data. .

The present invention has been made in view of such a point,
It is an object of the present invention to provide a backup circuit that can easily and reliably determine whether or not backup has been performed and that does not use stored data when backup has not been performed.

Means for Solving the Problems To achieve the above object, according to the present invention, when the supply of the main power supply voltage from the main power supply to the storage device is interrupted, the auxiliary power supply is supplied from the auxiliary power supply to the storage device. In a backup circuit of a storage device configured to retain stored data, a comparator that compares an auxiliary power supply voltage from an auxiliary power supply with a predetermined voltage when voltage supply from a main power supply is resumed, Means for making it impossible to access the storage device when it is detected that the voltage is lower than the predetermined voltage, and supplying the main power supply voltage to the memory side until the comparison is made by the comparator when the voltage supply is resumed. Means for avoiding this.

Operation According to such a configuration, when the voltage supply from the main power supply is restarted, it can be reliably determined whether or not the backup has been performed without using the check data or the memory from the system.

In addition, when the result of the determination is that the detected auxiliary power supply voltage is in a state of retaining data stored in the storage device, access to the storage device is enabled, but the detected auxiliary power supply voltage is If it is not in a state to hold the data stored in the storage device,
Since access to the storage device is disabled, unreliable data is not read.

An embodiment of the present invention will be described below with reference to the drawings. The same parts as those in the related art are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, when the voltage supply from the main power supply is resumed, the auxiliary power supply voltage Vs from the auxiliary power supply (9) is detected, and it is determined whether or not the auxiliary power supply voltage Vs is in a state of holding data in the memory (6). A determination means for performing the determination is provided, and is specifically configured as shown in FIG. That is, (10) compares the auxiliary power supply voltage Vs from the auxiliary power supply (9) with the reference voltage Vr when the main power supply terminal (1) supplies the main power supply voltage Vm when the voltage supply from the main power supply is resumed. A comparator that outputs a determination signal K indicating whether or not the backup has been performed based on the comparison result. The comparator (10) determines that the comparison result is Vs> Vr
In the case of (1), the determination signal K supplied from the signal output terminal (11) to the system side is set to the H level, and if Vs <Vr, the determination signal K supplied to the system side from the signal output terminal (11) is set to L.
Level. Here, the reference voltage Vr is
Vr> Vd is set so that there is a margin in the criteria for determining the backup status. (12) is a switch control circuit that outputs a switch control signal C2 based on the control signal C1 supplied from the comparator (10).
2) When the control signal C1 supplied from the comparator (10) becomes H level upon completion of the comparison between the auxiliary power supply voltage Vs and the reference voltage Vr, it is determined that the determination processing in the comparator (10) has been completed. Then, an H-level switch control signal C2 is output. (13) is closed only when the switch control signal C2 supplied from the switch control circuit (12) is at the H level, and is transmitted to the memory selection circuit (4), the memory (6) and the auxiliary power supply (9). Is a switch circuit that allows supply of the main power supply voltage Vm.

Therefore, when the voltage supply from the main power supply is restarted, the comparator (10)
When an H-level determination signal K is supplied to the system via the signal output terminal (11), the access control means (not shown) determines that the data stored in the memory (6) is retained, that is, backed up. An access signal CS1 is provided so that the stored data can be used again. If the supplied determination signal K is at L level, it is determined that the data has not been backed up and the data has been stored without providing the access signal CS1. Stop using data. The comparator (1
The switching circuit (1
Since 3) cuts off the supply of the main power supply voltage Vm, that is, separates the auxiliary power supply from the main power supply side, it is possible to reliably determine whether or not backup has been performed.

As described above, according to the backup circuit of the present invention, when the voltage supply from the main power supply is restarted, it is determined whether or not the data stored in the memory is retained, that is, whether or not the backup has been reliably performed. The determination can be made easily and reliably without using check data or memory.

If the result of the determination is that the detected auxiliary power supply voltage is in a state of retaining the data stored in the storage device, access to the storage device is enabled, but the detected auxiliary power supply voltage is If it is not in a state to hold the data stored in the storage device,
Since access to the storage device is disabled, unreliable data is not read.

[Brief description of the drawings]

FIG. 1 is a diagram showing a specific circuit configuration example of the present invention, and FIG. 2 is a diagram showing a conventional circuit configuration example. (1) Main power supply terminal, (6) Memory, (9)
Auxiliary power supply, (10) comparator, (12) switch control circuit, (13) switch circuit.

Claims (1)

(57) [Claims] An auxiliary power supply for supplying an auxiliary power supply voltage from the main power supply to the storage device when the supply of the main power supply voltage from the main power supply to the storage device is stopped, and holding the data stored in the storage device; In the backup circuit, when restarting the voltage supply from the main power supply, a comparator for comparing the auxiliary power supply voltage from the auxiliary power supply with a predetermined voltage, and when the auxiliary power supply voltage is detected to be lower than the predetermined voltage by the comparator Means for making the access to the storage device impossible, and means for preventing the main power supply voltage from being supplied to the memory side until the comparison is made by the comparator at the time of restarting the voltage supply. Backup circuit for storage device.