Switch interface for determining position of a plurality of switches using a determined time
First Claim
1. A switch interface, comprising:
- a first port for selectively outputting a lower and a higher voltage;
a second port;
a plurality of series combinations of a switch and a resistor which are connected in a parallel circuit, each of said plurality of series combinations having a unique resistance and each of said switches being in an open or closed position, said parallel circuit having a first node connected to said first port and a second node connected to said second port;
a capacitor connected between said second port and a node biased at a reference voltage;
means for determining a time for a voltage at said second port to increase to a predetermined voltage level when said first port changes state from said lower voltage to said higher voltage; and
means for determining said position of each of said switches in accordance with said time.
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Accused Products
Abstract
A circuit for interfacing switches to a component which allows the positions of the switches to be determined by the component. The component includes an input port and an output port. A switch network which is a parallel combination of two or more series combinations of a resistor and a switch is connected between the input and output port. A capacitor is connected between the input port and ground. The component determines switch positions by outputting a voltage on the output port and determining the time for the capacitor to charge to a predetermined value. Since each series combination has a unique resistance, the position of the switches therein can be determined in accordance with the capacitor charging time.
27 Citations
15 Claims
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1. A switch interface, comprising:
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a first port for selectively outputting a lower and a higher voltage; a second port; a plurality of series combinations of a switch and a resistor which are connected in a parallel circuit, each of said plurality of series combinations having a unique resistance and each of said switches being in an open or closed position, said parallel circuit having a first node connected to said first port and a second node connected to said second port; a capacitor connected between said second port and a node biased at a reference voltage; means for determining a time for a voltage at said second port to increase to a predetermined voltage level when said first port changes state from said lower voltage to said higher voltage; and means for determining said position of each of said switches in accordance with said time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of interfacing a plurality of switches to a component such that the component can determine the positions of each individual switch, the component having an input and an output port initially biased at a LOW voltage, the switch interface having a parallel combination of a plurality of series combinations of a switch and a resistor, the parallel combination being connected between the input and output port, each series combination having a unique resistance, and a capacitor connected between the input port and a node biased at a reference voltage, comprising the steps of:
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outputting a HIGH voltage on the output port; determining the time for the capacitor to charge to a predetermined voltage; and determining the positions of the switches in accordance with the time. - View Dependent Claims (12)
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13. A method of interfacing a plurality of switches to a component such that the component can determine the position of each individual switch, the component having an input and an output port initially biased at a LOW voltage. The switch interface having a parallel combination, of a plurality of series combinations of a switch and a resistor, the parallel combination being connected between the input and output port, each series combination having a unique resistance, and a capacitor connected between the input port and a node biased at a reference voltage, comprising the steps of:
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outputting a HIGH voltage on the output port; determining the time for the capacitor to charge to a predetermined level; outputting a LOW voltage on the output port; determining the time for the capacitor to discharge to a predetermined level; and determining the positions of the switches in accordance with the charging and discharging times. - View Dependent Claims (14, 15)
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Specification