General Magic, Inc.

Walter F Broedner

Anthony M Faddell

Stephen G Perlman

John E Watkins

Anthony M Fadell

A low power, single master, variable clock rate, daisy-chainable, serial bus connects a bus dispatch (master) to a chain of one or more daisy-chained peripheral devices (slaves). The bus has a bidirectional serial data line, a bidirectional clock line, unidirectional interrupt line, power and ground lines. A method for configuring the bus includes detecting connection and disconnection of a peripheral device to the bus. In the method, a last peripheral device on the bus is assigned the second status and all other peripheral devices on the bus are assigned the first status. Each peripheral device assigned the first status is configured to pass therethrough an interrupt signal on the bus. The last peripheral device is configured to invert an interrupt signal on the bus from a peripheral device that is newly attached to the bus. A peripheral device newly connected to the bus generates an interrupt signal that is inverted by the last peripheral device and transmitted over the bus to a host computer for the bus. Also, an interrupt signal is driven on the bus by one peripheral device on the bus upon disconnection of another peripheral device on the bus where the another peripheral device is downstream on the bus from the one peripheral device.

Method for configuring an intelligent low power serial bus

A low power, single master, variable clock rate, daisy-chainable, serial bus connects a bus dispatch (master) to a chain of one or more daisy-chained peripheral devices (slaves). The bus has a bidirectional serial data line, a bidirectional clock line, unidirectional interrupt line, power and ground lines. Each peripheral device includes a plurality of serial bus support structures. For example, the serial bus support structures can include an interrupt generation circuit, a power-on circuit, and a wake-up interrupt generation circuit, and a wake-up interrupt propagation circuit.

Support structures for an intelligent low power serial bus

A low power, single master, variable clock rate, daisy-chainable, serial bus connects a bus dispatch (master) to a chain of one or more daisy-chained peripheral devices (slaves). The bus has a bidirectional serial data line, a bidirectional clock line, unidirectional interrupt line, power and ground lines. All bus transactions over the bus occur under bus dispatch commands. If a peripheral device interrupts the bus dispatch, bus dispatch issues commands over the bus to determine which device caused the interrupt and what service is being requested by the device. The bus dispatch may then turn control of the data and clock lines over to the peripheral device for a limited amount of time depending on the service requested. New peripheral devices can be connected onto the bus and unused peripheral devices can be disconnected from the bus while the bus is operating without causing a bus failure. Similarly, bus dispatch may enter a low power sleep mode from which it may be awakened by a peripheral device. In some embodiments, additional lines such as battery charging lines and/or signal lines for other serial buses such as RS-232 and RS-422 are provided.

Method for transmitting bus commands and data over two wires of a serial

A low power, single master, variable clock rate, daisy-chainable, serial bus connects a bus dispatch (master) to a chain of one or more daisy-chained peripheral devices (slaves). The bus has a bidirectional serial data line, a bidirectional clock line, unidirectional interrupt line, power and ground lines. Each peripheral device includes a first bidirectional signal line, a second bidirectional signal line coupled to the bus clock and data lines, respectively, and an interface circuit coupled to the first and second bidirectional signal lines. The interface circuit includes a first buffer circuit coupled to the first and second bidirectional signal lines, and a second buffer circuit coupled to the first buffer circuit. A control circuit in the interface circuit couples the first and second buffer circuits where in a first mode of operation, the control circuit passes signals on the first and second bidirectional signal lines through the first and second buffer circuits, and in a second mode of operation, the control circuit passes signals on the first and second bidirectional signal lines through the first buffer circuit and configures the second buffer circuit to terminate the first bidirectional signal line. Thus bus power supply line is coupled to the interface circuit and a voltage on the power supply line is used to power the first and second buffer circuits and the control circuit. The bus interrupt line is coupled to the control circuit of the interface circuit. The interface circuit is also coupled to signal lines of the peripheral device.

Bus interface circuit for an intelligent low power serial bus

A low power, single master, variable clock rate, daisy-chainable, serial bus connects a bus dispatch in a base station (master) to a chain of one or more daisy-chained peripheral devices (slaves). The bus has a bidirectional serial data line, a bidirectional clock line, unidirectional interrupt line, power and ground lines. Data and commands are sent from the base station to a peripheral device, and data is received from the peripheral device by the base station by configuring each peripheral device on the bus to receive data and clock signals from the base station in an idle mode of operation. Upon a command send being transmitted by the base station, all peripheral devices on the serial bus between the base station and an addressed peripheral device remain in the idle mode and the addressed peripheral device is connected to the bus so that clock and data signals on the bus to are passed to the peripheral device. When the peripheral devices on the bus are in the idle mode of operation, and the base station transmits a command get to an addressed peripheral device, the addressed peripheral device and all peripheral devices between the addressed peripheral device and the base station are reconfigured to transmit clock and data signals from the addressed peripheral device to the base station.

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Saratoga, CA, United States of America

Walter F Broedner