Circuit card capable of switching between at least an N-bit...

Details Circuit card capable of switching between at least an N-bit... Circuit card capable of switching between at least an N-bit...

1998-11-24

2001-07-24

Lee, Thomas (Department: 2182)

Electrical computers and digital data processing systems: input/

Input/output data processing

Peripheral adapting

C710S105000, C348S222100, C348S236000

Reexamination Certificate

active

06266720

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a PC card capable of being plugged into a computer system, where the PC card is capable of switching between a 16-bit operation mode and a 32-bit operation mode. More particularly, the invention relates to a PC card capable of automatically switching operation modes upon being plugged into a card slot of a computer system.
2. Description of the Related Art
A PC card is a peripheral device developed for expanding capabilities of a personal computer (PC). PCMCIA (Personal Computer Memory Card Interface Association) and JEIDA (Japan Electronic Industry Development Association) have taken the initiative in prescribing mechanical and electrical specifications of PC cards. These specifications are hereby incorporated by reference. At present various kinds of PC cards are on the market, including memory cards, flash memory cards, HDD cards, and FAX/MODEM cards.
These PC cards are classified into 8-bit PC cards, 16-bit PC cards, and 32-bit PC cards, according to the width of an internal data bus. Currently marketed PCs have PC card slots provided therein for accepting various types of PC cards. However, PC card slots formed in some conventional PCs accept only a 16-bit PC card and a 32-bit PC card cannot be inserted into such a slot.
According to the above-mentioned specifications, a projection is provided in the vicinity of a PC card slot in order to identify the type of a PC card to be inserted into the slot. In this connection, a PC card has a groove formed therein in the vicinity of a connector thereof in order to receive the projection. The groove is sufficiently deep to accept the projection. The specifications dictate that a projection provided in a PC card slot dedicated to a 16-bit PC card be higher than that provided in a PC card slot dedicated to a 32-bit PC card. Accordingly, when a user attempts to insert a 32-bit PC card into a PC card slot dedicated to a 16-bit PC card, a projection provided in the slot prevents the insertion because the corresponding groove formed in the 32-bit PC card is too shallow to receive the projection. Since a drive voltage for a 32-bit PC card is 3.3 V, whereas that for a 16-bit PC card is 5 V, such a structural feature is appropriate for protecting an internal circuit of a card.
As the functions of PCs improve, the bus width of a PC card generally shifts from 8 bits to 16 bits and 32 bits. Currently released PC cards are most commonly of the 32 bit variety. However, many users still use PCs having a PC card slot dedicated to only a 16-bit PC card. According, if newly manufactured PC cards are adapted to operate in both 32-bit and 16-bit operation modes, they will be accepted by many more users.
However, because of the above-mentioned specifications, a 32-bit PC card cannot be inserted into a slot dedicated to a 16-bit PC card. Even when a groove formed in a 32-bit PC card is made deeper so that the 32-bit PC card can be inserted into a 16-bit PC card slot, neither the 32-bit PC card nor the associated PC can identify the 32-bit PC operation mode; thus, the 32-bit PC card cannot be operated properly.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a PC card which can select from among a plurality of operation modes associated with a plurality of data bus widths and which, when inserted into a PC card slot, can identify the type of the PC card slot and select the operation mode accordingly.
To achieve the above object, the present invention provides a PC card comprising: a circuit having a first function; a circuit having a second function; a selector for selecting either the first or second function; and a slot-type identification unit for identifying the type of PC card slot. The selector selects either the first or second function according to an identification signal received from the slot-type identification unit.
A typical PC card according to the present invention includes: a logic circuit which operates in a 16-bit mode; a logic circuit which operates in a 32-bit mode; a microprocessor; a microswitch provided on the PC card which, when inserted into a PC card slot, operates according to the shape of the PC card slot; and a signal line for transmitting an output from the microswitch to the microprocessor.
The shape of the PC card slot is a function of the width in bits of the card slot. Accordingly, when the PC card is inserted into the PC card slot, the make-break state of the microswitch changes depending on the shape of the PC card slot. The microprocessor identifies the state of the microswitch and switches the internal operation modes of the PC card accordingly. Thus, upon insertion of the PC card into the PC card slot, operation mode selection is completed within the PC card. Therefore, a user does not need to check for the type of PC card slot or to switch operation modes of a PC card.


REFERENCES:
patent: 5627416 (1997-05-01), Kantner
patent: 5708799 (1998-01-01), Gafken et al.
patent: 5911050 (1999-06-01), Egan et al.
patent: 5918202 (1999-06-01), Kuroki et al.
patent: 6088746 (2000-07-01), Koppa
patent: 0362050 (1990-04-01), None
patent: 08166906 (1996-06-01), None
patent: WO9614689 (1996-05-01), None

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