JPS6057572A - Sector creating circuit - Google Patents

Abstract

PURPOSE:To easily remove a short unusable final sector without changing a physical index signal and reduce the load of a control device by inhibiting a sector at the end section of a magnetic disk, etc. by means of a window signal which can be set freely. CONSTITUTION:A byte clock CLK is supplied to a sector generating counter circuit 10 and window generating counter circuit 12 and a byte/sector setting switch 14 sets a desired number of bytes per sector. A window generating setting switch 16 sets a byte number at which a window signal rises. If the number set by the switch 14 is the complement of N bytes, a carry output CA1 is produced when the counter circuit 10 counts the clock CLK for N bytes. If the number set by the switch 16 is the complement of Y bytes, another carry CA2 is produced when the counter circuit 12 counts the clock CLK for Y bytes. When the carry CA2 is produced, a gate 22 is closed and the carry CA1 which becomes a sector signal SCT is inhibited. By setting the Y bytes so that the CA2 is produced just before the final sector signal, the counter circuit 12 stops the operation when the CA2 is produced, and thus, the final sector is inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a sector creation circuit for a magnetic disk device.
The present invention relates to a sector creation circuit that has a function to prevent the final sector from being short when the number of bytes per sector is set by a switch.

Prior Art and Problems Magnetic disk drives store magnetic disks in a large number of concentric circles.
It is divided into i areas (trunks), each 1-rank is further divided into a plurality of small areas (sectors), and data is read and written in the sectors. Since the data unit differs depending on the user,
An effective method is to make the number of sectors per trunk variable (of course, if there are many sectors, the sector length will be small; if there are fewer, the sector length will be large) and be set in accordance with the requirements of each user. For this purpose, a sector creation circuit that can set the sector length with a switch has been developed, but in this method, sectors are created by sequentially cutting out the trunk from its starting point to the length determined by the switch. The final sector is likely to be short (if the track length is not an integral multiple of the sector length, the final sector will be short).

If the final sector becomes too short, the sector cannot be used, so it is an unnecessary sector from the perspective of the disk control device, but in the conventional device, the sector pulse of that sector cannot be inhibited on the disk device side. If you make the next sector pulse from the physical index signal that indicates the starting point of the trunk a logical index signal, ignore the original physical index signal, ignore the next sector pulse from the physical index signal, and use the sector pulse from the next one. , the first sector length is added to the final sector length, and the final sector length can be longer than other sector lengths, but
In this method, since the index signal differs from the original one, medium defect information expressed by the distance to the medium defect from the physical index signal must be converted into relative information from the logical index, which lacks versatility.

OBJECTS OF THE INVENTION The present invention leaves the index signal unchanged and inhibits the last sector pulse if the last sector is short to prevent the occurrence of a short sector.

Structure of the Invention The present invention provides a sector creation circuit comprising a counter that starts counting upon receiving an index signal indicating the starting point of a trunk of a magnetic disk, and outputs a sector signal for dividing a track into a plurality of sectors every time a predetermined number of sectors is counted. The present invention is characterized by the provision of a circuit for inhibiting the output of a sector signal to a designated sector of a track floor, which will be described in detail below with reference to embodiments.

Embodiment of the Invention FIG. 1 shows an embodiment of the invention, in which 10 is a sector creation counter circuit, 12 is a window creation counter circuit, and X4 is 1.
A switch 16 is a window creation setting switch for setting the number of bytes per sector.

CLK is a high I clock, INX is a physical index signal, and these are obtained from the servo surface of the disk device. The servo surface may be formed on a servo disk separate from the data disk, or may be formed within the data disk. 18 is an OR gate, 20 and 24 are inverters, and 22 is an AND gate, and the output of this AND gate becomes the sector signal SCT.

To explain the operation of this circuit with reference to FIG.
The sector setting switch 14 sets the desired number of hides per sector, and the window creation setting switch 16 sets the number of bytes at which the window signal will rise. The index signal INX is input to the load terminals of the counter circuits 10 and 12 via the OR gate 18 and the INHAK 20 (these counters are loaded with an L level signal), and the switch 14.1.
The value set in step 6 is sent to counters 10 and 12 by clock CL.
It is taken in in synchronization with K and starts the count amplifier. When the set number of the switch 14 is the complement of N by I, the counter circuit 10 overflows when counting N bytes of CLK and generates a carry output (, AI. This carry output CAI causes the AND gate 22 to open. If it is, it passes through the gate and becomes the sector signal SCT, and also passes through the OR gate 18 and inputs it to its own load terminal, so that the set value of the switch circuit 14 is taken in in synchronization with the clock CLK, and then the set value is counted again. start.

The same goes for the rest, and thus sector signals SCT of length N bytes set by the switch circuit 14 are generated one after another.

The counter circuit 12 takes in the set number of the switch 16 and starts counting, and if the set number is Y bytes? If the number is IIi, the counter 12 when counting the clock CL K.
overflows and produces a carry output CA2. Until now, there is no carry output CA2, so the inverter 24
Since the output of is at H level, the AND gate 22 is open. When carry output CA2 occurs, AND gate 2
2 is closed and the carry output CAI becomes the sector signal SCT.
is inhibited. The Y byte set by the switch 16 is
N < Z < (x + l) x for N
-1) Select so that N<Y<xN. In other words, the carry output CA2 is generated before the final sector signal. The carry output CA2 inverted by the inverter 24 enters the enable terminal EN of the counter circuit 12, and operates the counter when it is at IT level, and stops the counter operation when it is at L level. Therefore, when the carry output CA2 is generated (becomes H level), the counter circuit 12 stops operating, and resumes operation when the next index signal I N X is input. In this way, masking is performed for the final sector signal.

Generally, multiple disk devices are connected to a disk control device, and one of them has a large I-rack capacity (for example, a large disk diameter), and multiple disk devices have the same number of bytes. /sector is set, the number of sectors/track will naturally be large in a disk device with a large track capacity. This makes the control complicated, but in the present invention, the window creation setting switch 16
can be dealt with more easily. For example, if the Y hide set by the switch 16 is made small so that the carry output CA2 is generated before the last sector signal as shown by the dotted line in Figure 2, the number of sectors/tracks can be reduced. With this method, it is possible to easily make the number of sectors/tracks of disk devices under the same disk control device the same.

As described in detail, according to the present invention, unused sectors are inhibited by a freely settable window signal, so unnecessary or unusable sectors can be easily removed without the need to change physical index signals. This has the effect of reducing the load on the control device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart 1 to explain the operation. In the drawing, INX is an index signal, 10 is a counter, and S
CT is a sector signal, and 12, 16, 24, 22 is a sector signal output inhibit circuit. Applicant Fujitsu Limited Representative Patent Attorney Minoru Aoyagi

Claims (1)

[Claims] In a sector creation circuit that includes a counter that starts counting upon receiving an index signal indicating the starting point of a trunk on a magnetic disk and outputs a sector signal that divides the trunk into a plurality of sectors every time a predetermined number of sectors is counted, 1. A sector creation circuit for a magnetic disk device, comprising a circuit for prohibiting output of a sector signal to a sector.