Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral configuration
Reexamination Certificate
1998-10-29
2001-05-01
Lee, Thomas (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral configuration
C710S014000, C345S161000, C345S163000
Reexamination Certificate
active
06226696
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to integrated circuits, and in particular to a circuit that can be programmed to sense varying signals from different types of computer peripheral devices such as pointing devices.
The rapid expansion of the personal computer (PC) market has brought about a proliferation of PC peripheral devices. The range of these devices includes standard peripherals such as monitors, keyboards, modems, mouse and joystick devices, to CD ROM or DVD drives, and imaging devices such as printers and scanners, and to more advanced multi-media related devices such as high-fidelity audio and video products, data gloves and digitizers. In order to facilitate the interface between these wide ranging peripheral devices and the host PC, the members of the personal computer and telecommunications industry have developed a standard for a single, universal interface connector and protocol generally referred to as the Universal Serial Bus (USB). By defining a universal connector, the USB eliminates the need for different types of ports and jacks. It also eliminates the need to make provisions for installing different cards into dedicated PC slots and then reconfiguring the system in order to accommodate some of the enumerated peripheral devices. Further, interface between USB compliant PCs and peripheral devices is automatically configured upon physical connection.
While the USB has to a great extent standardized the interface protocol between the PC and the many different peripheral devices, there remains differences in the electrical specifications of the interface circuits. That is, while the same USB-defined set of signals may be involved in, for example, detecting a pointing device (e.g., mouse, joystick, trackball, gamepad, etc.), the circuits processing these signals may have differing electrical requirements. For example, the interface circuit for a mouse manufactured by one vendor may require an amount of sink current that is almost an order of magnitude smaller than one manufactured by another vendor. A similar incompatibility exists for different pointing devices manufactured by the same vendor. For example, the current sinking requirements for a joystick interface circuit differs substantially from those of a mouse roller. This results in manufacturers having to design different interface circuitry for the same USB compliant peripheral device, depending on the application and the vendor requirements.
There is therefore a need for a circuit that can accommodate differing interface electrical specifications for PC peripheral devices such as pointing devices as required by different manufacturers and different applications.
SUMMARY OF THE INVENTION
The present invention provides a programmable circuit capable of detecting pointing devices with varying interface electrical specifications. Broadly, the pointing device sensor of the present invention includes a programmable current sink circuit that is configured by a programming circuit. The programmable current sink circuit includes a plurality of individual programmable current sink blocks coupled to decode a corresponding plurality of roller input signals when configured in a roller mode of operation (e.g., mouse or trackball). Each programmable current sink block includes a plurality of switched current sink devices coupled to a comparator. A reference signal generator supplies a different reference signal to the comparators depending on whether the circuit is configured in a roller mode of operation or a joystick mode of operation.
Accordingly, in one embodiment, the present invention provides a programmable interface circuit for sensing computer pointing devices, wherein the interface circuit includes a programmable current sink circuit having a plurality of interface inputs coupled to receive signals from an external pointing device, and a programming circuit coupled to the current sink circuit by a control bus, wherein, control signals from the programming circuit configure the programmable current sink circuit to sink a different amount of current depending on the requirements of the external pointing device.
In a more specific embodiment of the programmable interface circuit of the present invention, the programmable current sink circuit includes a plurality of programmable current sink blocks each receiving a respective signal from the external pointing device, and a programmable reference signal generating circuit coupled to the plurality of current sink blocks, wherein the programmable reference signal generating circuit generates a first reference signal in a first mode of operation, and a second reference signal in a second mode of operation.
The following detailed description and the accompanying drawings provide a better understanding of the nature and advantages of the programmable interface circuit for sensing pointing devices according to the present invention.
REFERENCES:
patent: 4727514 (1988-02-01), Bhuva et al.
patent: 5379382 (1995-01-01), Work et al.
patent: 5526037 (1996-06-01), Cortjens et al.
patent: 5546030 (1996-08-01), Cameron
patent: 5550528 (1996-08-01), Offord et al.
patent: 5565889 (1996-10-01), Crooks et al.
patent: 6033441 (2000-03-01), Herbert
CY7C63100, CY7C63101 Universial Serial Bus conductor product information, Cypress Semiconductor Corporation, San Jose, CA 95134, Oct. 1996, rev. Nov. 1996.
Lin Feng-Chen
Sun Ni
Du Thuan
Fairchild Semiconductor Corporation
Lee Thomas
Townsend and Townsend / and Crew LLP
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