The present invention relates generally to digital serial interfaces, and more particularly, to universal serial bus (USB) interfaces wherein a digital serial interface is adapted for selecting between internal and external USB transceivers, and, additionally, the external USB transceiver may be electrically isolated from the digital serial interface and/or at some distance therebetween.
Digital devices may require galvanic (electric) isolation when coupling to a USB device. Isolation over a USB connection between a host device and a peripheral presently is complex and costly. An existing isolation technique is to use two microprocessor controllers. One microprocessor supports an application while the second microprocessor provides the USB interface and the host control. This solution is complex, costly and consumes additional power. It is also desired to communicate over longer distances than is available with a USB bus but still maintain the USB interface.
Therefore, there is a need for more flexibility, simplification, lower cost and power consumption when integrating USB communications between digital devices that may also require electrical isolation therebetween, and/or over longer distances.
The present invention overcomes the above-identified problems as well as other shortcomings and deficiencies of existing technologies by providing an apparatus, system and method for coupling an external USB transceiver to a USB interface module or use an internal USB transceiver with the USB interface module of a digital device. The digital device may have a digital processor comprising a microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), programmable logic array (PLA), and the like. The external USB transceiver may be easily electrically isolated from the serial interface. Galvanic (electric) isolation may be provided through optical isolation, transformer coupling, etc. The external USB transceiver may additionally be coupled to the USB interface module with a longer distance communications system then is specified under the USB standard. For example, fiber optics, radio signals, infrared, transformer coupling, etc., may be utilized to convey the serial digital signals between the external USB transceiver and the USB interface module. This longer distance communications system may also provide isolate between the external USB transceiver and the USB interface module. In addition the isolation and/or long distance communications system may have an simple and inexpensive single ended digital interface adapted for coupling to the external USB transceiver and the USB interface module.
When building digital devices it is highly desirable to integrate as much of the interface and communications modules into the digital device. Applications may then be configured with low cost internal modules, e.g., internal USB transceiver coupled to an internal serial interface, when electrical (galvanic) isolation of a USB connection is required, or when greater distances are required then is available under the USB specification an external, easily isolatable USB transceiver may be used. This allows more flexibility and thus a greater number of applications for which the digital device may be used.
Selection of either an internal or external USB transceiver to be used with a USB interface module of a digital device may be controlled by software, e.g., through a USB transceiver configuration bit in a configuration register of the digital device. The section of which USB transceiver will be used may also be done with a firmware bit in a non-volatile memory, e.g., flash memory, electrically erasable and programmable memory (EEPROM), fusible links, etc., that may control a data bus selection circuit, e.g., digital multiplexer adapted to connect either the internal or external USB transceiver to the USB interface module of the digital device. The digital device may be fabricated on an semiconductor integrated circuit die and this semiconductor integrated circuit die may be packaged in any type of integrated circuit package. It is contemplated and within the scope of the present invention that the semiconductor integrated circuit die may also be comprised of a plurality of semiconductor integrated circuit dice and may be packaged in a multiple die integrated circuit package.
A technical advantage of the invention is requiring only one USB interface module of a digital device for interfacing with either an internal or external USB transceiver.
Another technical advantage is lower cost to build and develop a digital device since more flexibility in USB interfacing is available without requiring extensive addition digital circuit functions.
Still another technical advantage is the ability to support industrial applications requiring electrical isolation with a low cost solution in a digital device.
A further technical advantage is the ability to have an operational external USB interface at longer distances from a digital device then is presently available at low cost.
Yet another technical advantage is selection of either an internal or external USB transceiver by setting or resetting a bit in a USB transceiver configuration register of a digital device.
Another technical advantage is selection of either an internal or external USB transceiver by setting or resetting a bit in a non-volatile memory of a digital device.
Other technical advantages should be apparent to one of ordinary skill in the art in view of what has been disclosed herein.
A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings wherein:
The present invention may be susceptible to various modifications and alternative forms. Specific embodiments of the present invention are shown by way of example in the drawings and are described herein in detail. It should be understood, however, that the description set forth herein of specific embodiments is not intended to limit the present invention to the particular forms disclosed. Rather, all modifications, alternatives, and equivalents falling within the spirit and scope of the invention as defined by the appended claims are intended to be covered.
Referring now to the drawings, the details of exemplary embodiments of the present invention are schematically illustrated. Like elements in the drawings will be represented by like numbers, and similar elements will be represented by like numbers with a different lower case letter suffix.
Referring to
The USB interface module 106 is coupled to multiplexer 108, wherein the multiplexer 108 is coupled to the internal USB transceiver 110 and is adapted to be coupled to the external USB transceiver 114. Optionally, the multiplexer 108 may be coupled to the external USB transceiver 114 through an isolation and/or distance interface 112. The interface 112 allows electrical isolation and/or increased distance between the external USB transceiver 114 and the digital device 102. The digital device 104 may control the multiplexer 108 over control line 120 for selecting between the internal USB transceiver 110 and the external USB transceiver 114 (optionally coupled through the interface 112). The control line 120 may be operative from a bit logic level in a register (not shown) or may be coupled to a firmware bit in a non-volatile memory (not shown), e.g., flash memory, electrically erasable and programmable memory (EEPROM), fusible links, etc.
The internal USB transceiver 110 is coupled to an input of the multiplexer 108 over an internal bus 122. The USB module 106 is coupled to the digital device 104 through a data bus 126 wherein the USB module 106 generates the appropriate timing, data and control signals in accordance with the USB specification. The internal USB transceiver 110 may be coupled to a USB port 118 and the external USB transceiver 114 may be coupled to a USB port 116. USB ports 116 and 118 may be the same or different USB ports. An input of the multiplexer 108 is adapted for coupling to the external USB transceiver over a simple digital bus 124, e.g., a bus having single ended logic levels. Since the interface 112 may be closely coupled to the digital device 102 through the bus 124, it does not need to be a low noise, low crosstalk differential bus like the USB specification requires of the USB ports 116 and 118.
The digital device 102 may be fabricated on an semiconductor integrated circuit die and this semiconductor integrated circuit die may be packaged in any type of integrated circuit package. It is contemplated and within the scope of the present invention that the semiconductor integrated circuit die may also be comprised of a plurality of semiconductor integrated circuit dice and may be packaged in a multiple die integrated circuit package.
The present invention provides support for both an internal (e.g., on-chip) USB transceiver 110 and an external (e.g., off-chip) USB transceiver 114. The external USB transceiver 114 may be used for applications where physical conditions dictate the location of the USB transceiver 114 to be located away from the digital device 102, and/or the USB transceiver 114 must be electrically (galvanic) isolated from the digital device 102. Electrical isolation of the external USB transceiver 114 may be achieved through well know techniques, e.g., opto-isolators, infrared, radio frequency, transformer coupling, etc.
Referring to
The present invention has been described in terms of specific exemplary embodiments. In accordance with the present invention, the parameters for a device may be varied, typically with a design engineer specifying and selecting them for the desired application. Further, it is contemplated that other embodiments, which may be devised readily by persons of ordinary skill in the art based on the teachings set forth herein, may be within the scope of the invention, which is defined by the appended claims. The present invention may be modified and practiced in different but equivalent manners that will be apparent to those skilled in the art and having the benefit of the teachings set forth herein.
This application claims priority to commonly owned United States Provisional Patent Application Serial Number 60/574,560; filed May 26, 2004; entitled “USB Transceiver Selection for Integrated Transceiver or Digital Interface First Device To USB Transceiver Second Device,” by Joseph Julicher, Igor Wojewoda and Mei-Ling Chen; which is hereby incorporated by reference herein for all purposes.
Number | Date | Country | |
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60574560 | May 2004 | US |