Bus maintenance circuit
AssigneeTexas Instruments Incorporated
InventorDerek Roskell
Life of this patent
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Abstract
A maintenance circuit for a bus (1) with a tristate driver (2) which includes a keeper circuit (3) having a first inverting logic gate (4) with an input connected to the bus (1) and a second inverting logic gate (5) with an input (6) connected to the output of the first logic gate (4). The output of the second logic gate (5) is restricted in current relative to that of tristate driver (2) and is connected directly to the bus (1). The keeper circuit (3) has a control input (7) for disabling positive feedback therein, such that the keeper circuit (3) acts as a pull-up or pull-down circuit.
Claims14
A circuit comprising,
- a bus,
- a tristate driver having its output connected to the bus, and
- a keeper circuit comprising,
- a first inverting logic gate means having an input connected to the bus, and
- a second inverting logic gate means having an input connected to the output of the first inverting logic gate means and an output restricted in current relative to that of the tristate driver and connected directly to the bus,
- wherein the keeper circuit has a control input for enabling or disabling positive feedback in the keeper circuit, and the circuit is such that when the positive feedback is disabled the keeper circuit acts as a pull-up or a pull-down circuit.
A keeper circuit comprising,
- a terminal, and
- a loop comprising,
- a first inverting logic gate means having an input connected to the terminal, and
- a second inverting logic gate means having an input connected to the output of the first inverting logic gate means and an output restricted in current relative to that of the first logic gate means and connected directly to the terminal,
- wherein the keeper circuit has a control input for enabling or disabling positive feedback in the keeper circuit, the first or the second inverting logic gate means having a second input connected to the control input, and the circuit being such that when the positive feedback is disabled the keeper circuit acts as a pull-up or a pull-down circuit.
Dependencies are inferred from the claim text.