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Abstract

An improved energy-saving keyboard with low parts count accomplishes a sophisticated regime of low-power mode intervals in response to key closures and communications from the computer to which the keyboard is connected. An interrupt pin of the keyboard controller (encoder) prompts the transition from low-power mode to normal mode. The communications from the computer is synchronous communications mediated by a clock line, and the interrupt pin is tied not to the clock line but to the data line of the synchronous channel. The interrupt pin is also tied to a resistor array providing pullup biases to the keyboard matrix; in normal-power mode a discrete output of the encoder forces the common point of the resistor array to a fixed voltage level. In low-power mode, on the other hand, the discrete output is not asserted, and the resistor array is pulled high by a pullup impedance of relatively high resistance to the fixed voltage level. In this way, any key closure at the keyboard triggers the interrupt. LEDs, if lit, are gradually dimmed in the absence of key activity, to conserve electrical power.

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First Claim