Universal serial bus peripheral bridge simulates a device disconnect condition to a host when the device is in a not-ready condition to avoid wasting bus resources
First Claim
1. A Universal Serial Bus to parallel bus bridge comprising:
- a D+ and a D−
serial bus connection;
a parallel bus connection; and
a serial bus disconnect circuit that senses the existence of a not-ready condition at said parallel bus connection, and responds to said not-ready condition by providing for a single-ended zero state on said D+ and D−
serial bus connections.
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Accused Products
Abstract
A Universal Serial Bus (USB) peripheral bridge and method for operation are disclosed. The bridge simulates a device disconnect condition to its upstream USB hub or host, even though it remains connected and powered, when its associated peripheral is not ready to communicate, powered off, or physically disconnected. For an IEEE-1284-1994 peripheral connection, the bridge senses the condition of the PLH peripheral line. If the PLH line is deasserted or floating, the bridge simulates a device disconnect condition by either allowing its upstream hub or host to take the D+ data line low, or taking the line low itself. By not allowing itself to be enumerated on the USB unless its associated peripheral is ready, the bridge avoids confusion at the host and wasted bus resources. At the same time, the bridge may remain physically connected to the host regardless of the state of the peripheral, even if the bridge is powered from the host.
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Citations
19 Claims
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1. A Universal Serial Bus to parallel bus bridge comprising:
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a D+ and a D−
serial bus connection;
a parallel bus connection; and
a serial bus disconnect circuit that senses the existence of a not-ready condition at said parallel bus connection, and responds to said not-ready condition by providing for a single-ended zero state on said D+ and D−
serial bus connections.
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2. A Universal Serial Bus to parallel bus bridge comprising:
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a D+ and a D−
serial bus connection;
a peripheral-device-ready signal parallel bus connection; and
a serial bus disconnect circuit connected to said peripheral-device-ready signal parallel bus connection, said serial bus disconnect circuit responding to a floating condition or a not-ready signal appearing at said peripheral-device-ready signal parallel bus connection by providing for a single-ended zero state on said D+ and D−
serial bus connections.- View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10)
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11. A Universal Serial Bus to IEEE-1284-1994 compliant parallel bus bridge comprising:
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a Universal Serial Bus port having a D+ connection, a D−
connection, a Vbus connection, and a serial bus ground connection;
an IEEE-1284-1994 compliant parallel port having a Peripheral Logic High signal connection; and
a serial bus disconnect circuit tied to said Peripheral Logic High signal connection, said serial bus disconnect circuit responding to a floating condition or a deassert signal appearing at said Peripheral Logic High signal connection by providing for a single-ended zero state on said D+ and D−
connections.- View Dependent Claims (12, 13)
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14. A method of operating a powered bridge between a Universal Serial Bus host and an IEEE-1284-1994 peripheral, said method comprising the steps of:
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indicating a device connect condition to said Universal Serial Bus host when said peripheral asserts its IEEE-1284-1994 Peripheral Logic High signal; and
indicating a device disconnect condition to said Universal Serial Bus host when said peripheral deasserts or floats its IEEE-1284-1994 Peripheral Logic High signal, or when said peripheral is physically disconnected from said bridge. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification