US 5,179,577 A · Dynamic threshold data receiver for local area networks

Abstract

A dynamic threshold data receiver uses a single comparator for both squelch and data detection. The comparator has a high-magnitude threshold when the receiver is squelched and a low-magnitude threshold when the receiver is unsquelched. A squelch signal is provided by squelch control logic responsive to a comparison signal from the comparator. The squelch control logic has an interval timer comparing intervals of the comparison signal to a predetermined duration of time, and the squelch control logic changes the squelch signal from the asserted state to the unasserted state after the interval timer determines that the magnitude of the signal level on the comparator input has exceeded the high-magnitude threshold for at least said predetermined period of time. Preferably the squelch signal is not asserted until two transitions occur in the comparison signal after the high-magnitude threshold has been exceeded for the predetermined period of time, and the squelch signal is reasserted when a transition fails to occur in the comparison signal for a predetermined duration of time. Preferably the comparator is a differential line receiver, and each of the high and low magnitude thresholds has hysteresis.

Claims20

Dependent claims

A method of adjusting the threshold of a comparator for detecting data, said comparator having an input receiving a data signal and an output providing a comparison signal indicating a comparison of signal level on said input to said threshold, said method comprising the steps of:

(a) setting said threshold to a predetermined high magnitude;
and then
(b) inspecting said comparison signal to determine when said signal level on said input has a magnitude exceeding said high magnitude for a period of time greater than a predetermined period of time;
and then
(c) after said inspecting of said step (b) determines that said signal level on said input line has a magnitude exceeding said high magnitude for a period of time greater than said predetermined period of time, changing said threshold to a predetermined low magnitude;
and then
(d) outputting data from said comparison signal when said threshold is set to said low magnitude.

4 more elements

A dynamic threshold data receiver comprising, in combination:

a comparator having a data signal input line, a threshold control line, and an output line providing a comparison signal, said comparison signal indicating a comparison of signal level on said input line to a threshold, said threshold being set to a high magnitude when a squelch signal is asserted on said threshold control line, and said threshold being set to a low magnitude when said squelch signal is not asserted on said threshold control line;
and
squelch control logic connected between said output line and said threshold control line, said squelch control logic including an interval timer responsive to said comparison signal for comparing intervals of the comparator signal to a predetermined period of time, and state logic connected to said interval timer for asserting said squelch signal and changing said squelch signal from an asserted state to an unasserted state after said interval timer determines that said comparison signal has indicated that the magnitude of the signal level on the input line has exceeded the high magnitude for at least said predetermined period of time.

A dynamic threshold data receiver comprising, in combination:

a differential comparator having a pair of data signal input lines, a threshold control line, and an output line providing a comparison signal, said comparison signal indicating a comparison of differential signal level between said input lines to a threshold, said threshold being set to a high magnitude when a squelch signal is asserted on said threshold control line, and said threshold being set to a low magnitude when said squelch signal is not asserted on said threshold control line;
and
squelch control logic connected between said output line and said threshold control line, said squelch control logic including an interval timer responsive to said comparison signal for comparing intervals of the comparison signal to a predetermined period of time;
an activity timer responsive to said comparison signal for detecting an absence of changes in said comparison signal over a predetermined duration of time;
and state logic connected to said interval timer and said activity timer for changing said squelch signal from an asserted state to an unasserted state after said interval timer determines that said comparison signal has indicated that the magnitude of the signal level on the input line has exceeded the high magnitude for at least said predetermined period of time, and changing said squelch signal from said unasserted state to said asserted state after said activity timer detects an absence of changes in said comparison signal over said predetermined duration of time.

2 more elements

Dependencies are inferred from the claim text.

Dynamic threshold data receiver for local area networks

Life of this patent

Dynamic threshold data receiver for local area networks

Life of this patent

Abstract

Claims20