COMPOSITE MEMORY DEVICE

Abstract: Disclosed is a composite memory device which comprises a recording disc medium (31) having a large number of recording tracks to and from which data is written and read, a housing (30) for holding the recording disc medium (31), a rewritable semiconductor memory (37) disposed within a portion of the housing (30), and pins (38) disposed within a portion of the housing (30) for transferring data between the semiconductor memory (37) and an external device.

Description: The present invention relates to a composite memory device which, by including two kinds of memory, enables a reduction in access time. One kind of memory is a magnetic or optical disk which requires a relatively long access time to read data recorded on a recording track of the disk or to write data on a recording track thereon, the other is semiconductor memory adapted to contain data for use in accessing files on the disk. Magnetic or optical disks are formatted to enable data to be recorded thereon. Fig. 1 shows one example of the format of a magnetic recording medium or disk. The disk has several tracks 15, 16, each of which being divided into several sectors 13, 14. The tracks 15, 16 and the sectors 13, 14 are allocated track addresses and sector addresses, respectively, and are adapted to contain data. Fig. 2 shows one example of the relationship between tracks and sectors. The tracks are called track 0 (17), track 1 (18), track 2 (18) ... in order from the outer periphery of the magnetic recording disk, track 0 (17) defining a directory area used to locate file data recorded on the magnetic recording disk, track 1 (18), track 2 (18) . . . after track 0 defining file areas. When data in a certain file area is to be read, a head of an external unit such as a disc drive unit (hereinafter referred to as a disc drive) is first moved to the directory area to read the track and sector addresses corresponding to the track of the data which is to be read, then the head is shifted to the corresponding file area to read the data. In the abovedescribed arrangement, the time required for the disc drive to access the data is relatively long on average, up to about 100 milliseconds. It has been proposed, in JP-A-60-15880, upon which is based the prior art portion of claim 1, to provide a composite memory device capable of overcoming the above-mentioned disadvantage of the conventional arrangement of discs, that is, a composite memory device which has a very short access time even when the disc has a large memory capacity. A rewritable non-volatile semiconductor memory is incorporated in a memory device which includes a recording disc medium, for storing therein directory data. Such semiconductor memories normally have access times of about ten to several hundreds of nanoseconds, which are much shorter than those of conventional memory devices using magnetic or optical discs in which seek times include the time required for mechanically shifting the head and the time required for searching for the data or recording area. In consequence, the access speed of the composite memory device is increased, even if the memory device has a large recording capacity, since at least the contents of the directory are stored in a semiconductor memory which has a relatively short access time, to enable location of the data file areas. A difficulty which can arise with such a memory device derives from the exposed nature of the terminal pins. The present invention, as defined in claim 1, for the purpose of preventing the damage caused by static electricity, has a mechanism which exposes semiconductor memory terminals so that they can be connected to the connector provided on the disc drive when the composite memory device is loaded into the disc drive, and which screens them by a protection plate so that they cannot be touched by human body when the composite memory device is removed from the disc drive. When such a mechanism is provided on the composite memory device, the disc drive naturally must be provided with a mechanism which removes the protection plate and exposes the semiconductor memory terminals which have been covered by the plate. This, however, increases the production costs of the disc drive and the composite memory device. Generally, the recording medium of a composite memory device is housed in a disc-shaped recording medium casing in order to prevent it from being damaged by contact with the human body, and is exposed only through a head entry aperture opened in a portion of the casing and provided with a shutter. The shutter exposes the recording medium through the head entry aperture when the composite memory device is loaded into the disc drive, and covers the head entry aperture when the memory device is removed from the disc drive by being slid to a position at which it screens the recording medium. The function of the mechanism of the shutter satisfies the requirement of the protection plate mechanism which protects the semiconductor memory from damage by static electricity. In other words, the semiconductor memory terminals are disposed in the housing at a position at which they are screened by the shutter when the shutter covers the head entry aperture and at which they are exposed when the shutter opens the head entry aperture. In this way, the terminals for the semiconductor memory can be prevented from making contact with the human body, like the disc-shaped recording medium, and the handling of the composite memory device can be improved without increasing the production costs. In order to facilitate such screening and protection of the terminals, they are provided as track contents or pads mounted on the upper and.or lower surface of the housing where they are readily connected responsive to insertion of the memory device into a disc drive. Brief Description of the Drawings The present invention will be described hereinbelow by way of example which does not specifically limit the scope of the present invention, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a conventional magnetic disc medium, explaining the formatting thereof; Figure 2 illustrates the relationship between tracks and sectors shown in Figure 1; Figures 3 and 4 are perspective views of a composite memory device in which a slidable shutter is opened and closed, respectively, showing an embodiment of the present invention; and Figures 5 and 6 are perspective views of a composite memory device, showing a second embodying of the present invention. Fig. 3 is a perspective view of an embodiment of the composite memory device according to the present invention which comprises what is called a 3.5-inch micro-floppy disc cartridge which employs as a disc-shaped recording medium 12 a magnetic disc. The disc-type recording medium 12 is housed within a housing 1. A central portion of the housing 1 is provided with an aperture 5 through which a hub 6 fixed to the center of the recording medium 12 is exposed, the disc-type recording medium 6 being rotated through the hub 6 when the disc cartridge is loaded into the disc drive. Each side of one edge of the housing 1 is provided with a recess 3 and a head entry aperture 23. A shutter 2 is mounted in such a manner as to be slidable along the surfaces of the housing within the recesses 3 so as to expose and screen the head entry aperture 23. A portion of the shutter 2 is provided with a head entry aperture hole 4 which is substantially aligned with the head entry aperture 23 when the shutter opens the head entry aperture. A semiconductor memory or semiconductor memory/processor (hereinafter referred to as a semiconductor memory) is mounted in a portion of the housing 1, and a plurality of terminal pins shown as contact pads 27a, 27b, 27c, 27d ..., which connects the semiconductor memory 9 to an external circuit are provided on a portion of the recess 3. Fig. 9 shows a composite memory device in the state wherein the shutter 2 is moved in the direction indicated by an arrow A and the head entry aperture hole 4 is substantially aligned with the head entry aperture 23 as the composite memory device is loaded into the disc drive. Fig. 10 shows the composite memory device in the state wherein the shutter 2 is moved in the direction indicated by an arrow B so as to screen the head entry aperture 23. The pins 27a, 27b ... are positioned at a location at which they are completely exposed from the housing 1 in the state shown in Fig. 3 and at which they are completely screened by the shutter 2 in the state shown in Fig. 4. In consequence, the pins are electrically connected to the signal connector (not shown) provided on the disc drive without any problem in the state shown in Fig. 3 so as to transfer signals between the disc drive and the semiconductor memory, to be grounded and apply power source voltage. In the state shown in Fig. 4 wherein the composite memory device is removed from the disc drive, the pins may contact with human body. However, most of the pins are screened by the shutter 2 and are thereby protected from the damage caused by the static electricity. If the shutter 2 is made of a conductor such as a metal, it is preferable for the shutter 2 to be grounded while the composite memory device is loaded into the disc drive. All of the pins 27 for the semiconductor memory may not be able to be located in the area at which they can be screened by the shutter 2. In such a case, a pin which withstands impact caused by the static electricity, such as a ground pin, may be disposed at a location at which it is exposed, as shown in Fig. 4 Of couse, this is a most extreme measure. The size or arrangement of the pins should be studied so that the pins are all screened by the shutter so as to prevent soiling of the pins by the contact with the human body and to make the handling of the composite memory device more convenient. The semiconductor memory 9 may be located at a location other than that shown in Figs. 9 and 10, so long as it can be electrically connected to the pins 27 and at a location which it does not make contact with the disc-shaped recording medium. The number and shape of the pins 27 are not limited to those shown in the figures. In short, they may be provided at a position at which they are exposed when the composite memory device is loaded into the disc drive and at which a required number of them are screened by the shutter when the device is removed from the disc drive. Fig. 5 is a perspective view of a second embodiment of a composite memory device according to the present invention, in which the present invention is applied to an optical disc cartridge which employs as a disc-shaped recording medium 31 an optical disc. The optical disc cartridge is essentially constructed by a housing 30 made of a synthetic resin, the disc type recording medium 31 rotatably housed within the housing (a cartridge casing), and a shutter formed by bending a metal thin plate in an inverted shape. The housing 30 consists of an upper and lower thin casings which are joined together to form a central space used to house the disc type recording medium 31 and other components. The surface of the housing 30 is provided with a head entry aperture 33 through which an optical head accesses the disc-type recording medium 31. The head entry aperture 33 is normally screened by the shutter 32 so as to protect the recording medium. The shutter 32 is formed by bending a metal thin plate such as a stainless thin plate, into an inverted shape. It is slidable along the surfaces of the housing so as to be moved to a position at which it exposes the head entry aperture 33 when the composite memory device is loaded into the disc drive. The disc-type recording medium 31 comprises an optical disc on the two sides of which optical data are recorded. Normally, the recording medium 31 is stationarily housed within the housing, and becomes rotatable by a mechanism (not shown) when the composite memory device is loaded into the disc drive and the shutter opens the head entry aperture. The optical disc which has been schematically described in the above has been disclosed in the specification of Japanese Patent Laid-Open No. 150963/1983 (publication No. JP-A-60043279) by the present applicant, and detailed description thereof is therefore omitted. The optical disc cartridge of this invention incorporates a rewritable non-volitale semiconductor memory which stores the directory data used to access the data stored in the optical disc, and the pins for the semiconductor memory are located on the wall of the housing at a location at which they are screened by the shutter 32 when the shutter screens the head entry aperture 33. Fig. 5 shows the composite memory device in the state wherein it is removed from the disc drive and in which the shutter 32 is located at the center of recesses 39 of the housing 30 so as to screen the head entry aperture 33. Pins 38 are disposed on the wall of the housing which is screened by the shutter 32 in that state. Fig. 12 is a perspective view of an essential part of the composite memory device of Fig. 5 which is loaded into the disc drive. The shutter 32 slides in the direction indicated by an arrow C so as to open the head entry aperture 33. In this state, the pins 38 are all exposed and are electrically connected to the signal connector (not shown) provided on the disc drive so as to process signals. The semiconductor memory 37 is provided at a location at which it can be electrically connected to the pins and at which it does not contact with the disc type recording medium when it is rotated. Fig. 6 shows one example of the location of the semiconductor memory. If the disc-type recording medium 31 is of a type on which data can be recorded on two sides, the semiconductor memory 37 and the pins are provided on the front and back of the housing, respectively, one for each surface, so as to store the directory data for the corresponding surface alone. The shape, the number, and the location of the pins 38 are not limited to those shown in Fig. 6, but various modifications are possible. The rewritable semiconductor memory is incorporated in the optical disc cartridge. However, if the optical disc employed is a read-only disc, a read-only type semiconductor memory may be used accordingly. Commercially available semiconductor devices, each of which is composed of an IC memory chip and a CPU may be used as a semiconductor memory of this invention, together with a back-up battery, if necessary. It will be appreciated that in a composite memory device arranged in any of the abovedescribed manner, the shutter prevents the pins from coming into contact with the human body. This could cause a serious problem particularly in a dry winter season when static electricity tends to be charged in the human body, because the charged static electricity might change or destroy the data stored in the semiconductor memory, without the protection given against such contact. The semiconductor housing has been shown positioned at a location at which it does not interfere with the disc l2 housed within the housing 1. However, it may be disposed at any position other than that shown in Figure 3, so long as the semiconductor memory can be connected to the connector provided on the disc drive when the disc cartridge is loaded into the disc drive. When the thus-arranged composite memory device is loaded into a disc drive which is designed to suit it, the disc drive accesses the directory stored in the semiconductor memory in response to, for example, the data read instruction from a host computer, and moves to a head to a track when is recognised by the access so as to access the data stored in the corresponding sector. Therefore, an access time required for a track and a sector accesses can be greatly reduced when compared with that of the conventional disc in which the directory area in one of the tracks is accesses. In consequence, the access time of the disc memory becomes substantially equal to the time required to access the track of the file area, reducing the overall access time greatly.

Claims: A composite memory device comprising a disc type recording medium (12,31) having a large number of recording tracks (18) in and from which data is written or read, a housing (1,30), which has generally planar upper and lower surfaces, holding said recording medium, and a rewritable semiconductor memory (9,37) located in a portion of the housing at which the semiconductor memory does not interfere with the disc type recording medium, the housing having a head entry aperture (23,33) for access of a signal transfer head to the recording medium, terminals (27,38) to the outside of the housing being provided for the transfer of signals between the semiconductor memory and an external device, characterised in that the terminals are contact pads and are provided on at least one of the upper and lower surfaces of the housing, the aperture (23,33) is shieldable by a shutter mounted on the housing in such a manner as to open or close the head entry aperture by sliding along the surface of the housing, and in that at least some of the terminals are covered by the shutter (2,32) when it is in its head entry aperture covering position but being exposed when the head entry aperture is exposed. A composite memory device according to claim 1, wherein said disc type recording medium comprises a magnetic disc (12). A composite memory device according to claim 1, wherein said disc type recording medium comprises an optical disc (31).

Inventors: OZEKI, TOMOTAKA
Applicants: HITACHI MAXELL LTD.
Application year: 1987
Main classification: G11B23
IPC codes: G11B23, G11B27