Method and apparatus for compensated slew rate control of line termination

A method comprising:

• driving a last voltage level corresponding to a last signal onto a transmission line through a driver circuit;
• releasing control of the transmission line;
• disengaging the driver circuit;
• and
• engaging a termination circuit at a controlled slew rate by providing a slew rate controlled input voltage to the termination circuit.

A digital system comprising:

• a transmission line;
• a first component connected with the transmission line to receive or to transmit signals on the transmission line, the first component including a line termination circuit connected with the transmission line and a slew rate control circuit to engage or disengage line termination at a controlled slew rate by providing a slew rate controlled input voltage to the line termination circuit of the first component;
• and
• a second component to receive or to transmit signals on the transmission line, the second component including a line termination circuit connected with the transmission line and a slew rate control circuit to engage or disengage line termination at a controlled slew rate by providing a slew rate controlled input voltage to the line termination circuit of the second component.

An apparatus comprising:

• a charge accumulation node;
• slew control means for accumulating a charge at said charge accumulation node to a first voltage level at a controlled rate;
• activation means for switching current flow between said charge accumulation node and a termination control input;
• and
• termination means for engaging or disengaging line termination at a controlled slew rate in response to a voltage level received on said termination control input.

A method comprising:

• employing a driver circuit to charge a transmission line terminal to a last voltage level corresponding to a last transmission signal;
• releasing control of the transmission line;
• disengaging the driver circuit;
• and
• adjusting a termination circuit coupled to the transmission line terminal from a first impedance level to a second impedance level, differing from the first impedance level, wherein the adjusting is performed at a slew rate selected from a plurality of slew rates.

A method comprising:

• receiving a last voltage level corresponding to a last transmission signal at a transmission line terminal;
• requesting control of the transmission line;
• disengaging a termination circuit;
• and
• engaging a driver circuit to charge a transmission line terminal to a same voltage level corresponding to the last transmission signal by adjusting a charge on an input to the driver circuit from a first voltage level to a second voltage level, differing from the first voltage level, wherein the adjusting is performed at a controlled slew rate.

A digital system comprising:

• a transmission line;
• a first component connected with the transmission line to receive or to transmit signals on the transmission line, the first component including a line termination circuit connected with the transmission line and operatively coupled with a slew rate control circuit to engage line termination at a controlled slew rate;
• and
• a second component to receive a last voltage level corresponding to a last transmission signal on the transmission line, the second component including a line termination circuit connected with the transmission line and operatively coupled with a slew rate control circuit to disengage line termination and to engage a driver circuit to charge the transmission line to a same voltage level corresponding to the last transmission signal by adjusting a charge on an input to the driver circuit from a first voltage level to a second voltage level, differing from the first voltage level, wherein the adjusting is performed at a controlled slew rate.

A method for making a communication device comprising:

• connecting a first switching device of a first impedance range with a first voltage source and with a charge collecting node to conduct a current between the first voltage source and the charge collecting node;
• connecting a second switching device with the charge collecting node and with a slew rate controlled activation input of a line termination device of a second impedance range to conduct a current between the charge collecting node and the slew rate controlled activation input;
• and
• connecting the termination device with a second voltage source and with a transmission line terminal to transition from a high impedance of the second impedance range to a lower impedance of the second impedance range at a controlled slew rate and to conduct current between the second voltage source and the transmission line terminal responsive to a signal received on its slew rate controlled activation input.