JPH0582665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device with improved reliability.

Magnetic disk drives have advantages such as extremely short access times compared to magnetic tape drives, and the ability to store recorded information permanently as long as it is not rewritten compared to semiconductor storage devices, so they are used as external storage devices for data processing equipment. occupies a central position.

Further, as shown in FIG. 2a, the magnetic disk device 1 is normally connected to a higher-level control device, such as a magnetic disk control device 2, by a command cable 3 and a data cable 4, and the magnetic disk device Data is written on the magnetic disk or data recorded on the magnetic disk is read according to the command given from 2.Writing or reading commands (commands)
are sent and received via the command cable 3, and write data and read data are sent and received via the data cable 4.

In addition, 11, 12, 13, 14, 15 and 1
6 is a component of the magnetic disk device 1; 11 is a component of the magnetic disk device 1;
1 is a driver receiver circuit (D/R circuit) connected to the command cable 3, 12 is a control circuit that controls each part, 13 is a variable frequency oscillator (VFO), and 14 is a read/write control circuit that performs read/write control ( R/W control circuit), 15 is a read/write clock signal generation circuit (R/WC generation circuit) that generates a read/write clock signal, 16
is a driver receiver circuit (D/R circuit) connected to the data cable 4.

Further, 21, 22, 23, 24 and 25 are components of the control device of the magnetic disk control device 2, 21 is a driver receiver circuit connected to the data cable 4, and 22 is a write clock signal generator for generating a write clock signal. circuit (WC creation circuit), 23 is a write data creation circuit (WD creation circuit) that creates write data, 24 is a control circuit that controls each part, 25 is a driver receiver circuit (D/R circuit).

[Conventional technology]

Magnetic disk device 1 and magnetic disk control device 2
The transfer of write data and read data between the magnetic disk drive 1 and the magnetic disk drive 1 is performed in synchronization with a VFO clock signal (see the time chart in Fig. 2b, hereinafter the same) generated by the variable frequency oscillation circuit 13 built into the magnetic disk drive 1. However, in order to exchange read data and write data on the magnetic disk control device 2 side, or to create write data in the write data creation circuit 23 of the magnetic disk control device 2, the clock signal synchronized with the VFO clock signal is reversely clocked. It is necessary to receive it from the magnetic disk device 1 side.

For this reason, the read/write clock signal generating circuit 15 of the magnetic disk device 1 generates a read/write clock signal as a clock signal synchronized with the VFO clock signal, and sends this to the magnetic disk controller 2.

Also, when writing data, the write data synchronized with the read/write clock signal sent from the magnetic disk device 1 is sent to the magnetic disk controller 2.
is created by the write data creation circuit 23 of
Along with this write data, a read/write clock signal sent from the magnetic disk device 1 is sent back from the magnetic disk controller 2 to the magnetic disk device 1 as a write clock signal only for the time required for the write operation.

It is desirable that the write clock signal sent back to the magnetic disk device 1 is kept in synchronization with the VFO clock signal, but in reality, as illustrated in the time chart in FIG. Receiver circuit (D/R
delay t1 in the driver of circuit) 16, delay t2 in the data cable 4, delay t3 in the receiver of the driver receiver circuit 21 of the magnetic disk controller 2 and inside the magnetic disk controller 2, driver receiver circuit 21 of the magnetic disk controller 2 A delay t4 in the driver and a delay t5 in the receiver of the driver-receiver circuit 16 of the magnetic disk device 1 occur.

Therefore, in the read/write clock signal generating circuit 15, in addition to the read/write clock signal, the clock signal A and the clock signal B, which have the relationship as shown in the time chart of FIG.
In order to correctly capture the write data, the read/write control circuit 14 of the magnetic disk device 1 receives the write data sent in synchronization with the trailing edge of the write clock signal at the leading edge of the clock signal to be written. The write data' is created by retaking the data, and at the same time, in order to synchronize the VFO clock inside the magnetic disk drive with the write data', the received write clock signal and
By comparing the phase difference with the VFO clock signal, if the leading edge of the write clock signal matches the "0" level of the VFO clock signal, the clock signal A is set.
If it matches the "1" level of the VFO clock signal, the write data ' is taken using the clock signal B and the write data is created.

Note that it takes a delay time t1...t2... to read the write data to '' and from '' again.
This is because the total time T of t5 is uncertain due to the cable length, variations in elements, and the like.

Write data synchronized with the VFO clock is
After that, it is sent to the modulation circuit inside the R/W control circuit 14.

[Problem that the invention seeks to solve]

In the device with the above configuration, the internal circuit of the magnetic disk control device 2 and the driver receiver circuit 2
If the write clock signal does not reach the read/write control circuit 14 of the magnetic disk device 1 due to a failure on the driver side of the magnetic disk device 1, the write data cannot be read again at the leading edge of the write clock. There was a problem that the write data could not be written correctly.

[Means for solving problems]

According to the present invention, the above problem can be solved by reading and writing data in a magnetic disk device under the control of a magnetic disk control device. In the disk control device, write data is created, and a write clock signal is generated only for the time required for the write operation, and is sent to the magnetic disk drive prior to a write command, and the magnetic disk drive receives the write data at the leading edge of the write clock. In the re-implemented configuration, the magnetic disk drive is provided with a write clock signal detection circuit, which delays the write command by a predetermined time, and which is set by the leading edge of the write clock signal and the write command to detect the signal. and a circuit that generates a signal set by this signal and the delayed write command, and generates an alarm signal if the write clock signal is not received prior to the delayed write command. This problem is solved by a magnetic disk device that prevents data from being written to the magnetic disk.

[Effect]

That is, in the present invention, prior to writing, it is checked whether or not a clock signal is being received from the host control device, and if the clock signal is not being received, an alarm signal is generated to prevent writing. It is something.

〔Example〕

The gist of the present invention will be specifically explained below with reference to an embodiment shown in FIG.

FIG. 1a is a block diagram showing the configuration of an embodiment of the present invention, and the same reference numerals as those in the conventional example in FIG. 2a refer to the same objects, and 17 is a write clock signal detection circuit (WC detection circuit). be.

FIG. 1b shows the write clock signal detection circuit 1.
7, in which 25 is a delay circuit that delays the write command WT given by the control circuit 12 by a predetermined time, and 26 is a delay circuit that receives the write command WT and receives the write command WT according to the first leading edge of the write clock signal WC. D-shaped flip-flop, 27
is a D-type flip-flop which receives the output of the negative terminal Q of the flip-flop 26 and is set by the output WT' of the delay circuit 25.

FIG. 1c is a time chart explaining the operation of the above embodiment, where WC is the same write clock signal as in FIG. Output of negative terminal *Q, WT' is delay circuit 2
5, AL indicates an alarm signal issued from flip-flop 27.

As shown by the solid line, if the write clock signal WC is received before the write command WT, the output of the flip-flop 26 is "0", and therefore the output AL of the flip-flop 27 is "0".
In other words, no alarm signal is generated.

Further, as shown by the dotted line, if a predetermined time has elapsed after receiving the write command WT and the write clock signal WC is not received before the delayed write command WT' is output from the delay circuit 25, The output of the flip-flop 26 is "1", therefore the output AL of the flip-flop 27 is "1", that is, an alarm signal is generated, and the control circuit 12 takes a write-inhibiting action.

〔Effect of the invention〕

As described above, the present invention has the effect of preventing data loss caused by writing without using a write clock signal and improving the reliability of the magnetic disk device.

[Brief explanation of the drawing]

FIG. 1a is a block diagram showing the configuration of an embodiment of the present invention, FIG. 1b is a concrete configuration example of the main part of the embodiment, and FIG. 1c is a time chart explaining the operation of the embodiment. Figure 2a is a circuit diagram of the conventional example, Figure 2b
is a time chart explaining the problems of the conventional example. In the figure, 1 is a magnetic disk device, 2 is a magnetic disk controller, 17 is a write clock signal detection circuit, 25 is a delay circuit, and 26 and 27 are flip-flops.

Claims (1)

[Claims] 1 Reading and writing of data in a magnetic disk device is performed under the control of a magnetic disk controller, and when writing data, the magnetic disk controller writes data in synchronization with a read/write clock signal from the magnetic disk device. At the same time, a write clock signal is generated only for the time required for a write operation, and is sent to the magnetic disk drive in advance of the write command, and the magnetic disk drive retakes the write data at the leading edge of the write clock. The disk device is provided with a write clock signal detection circuit, which includes a circuit for delaying a write command for a predetermined period of time, a circuit for generating a signal set by the leading edge of the write clock signal and the write command, and a circuit for generating a signal in response to the leading edge of the write clock signal and the write command. If the write clock signal is not received prior to the delayed write command, it generates an alarm signal and prevents data from being transferred to the magnetic disk. A magnetic disk device characterized by blocking writing.