Set-reset (S-R) latch based deglitch circuit
Methods and systems that use a simple hardware circuit and/or digital logic solution to identify and remove both positive and negative glitches from a signal. For this hardware circuit and/or digital logic solution, a glitch is referred to as an unwanted pulse with a width less than a specified duration, and is generally caused by noise or improper operation by other devices. A positive glitch occurs when the input signal has been logic low for some time, while a negative glitch occurs when the input signal has been logic high for some time. In one embodiment, the hardware circuit and/or digital logic solution removes noises from signals transmitted between a digital circuit and its switches and/or remote sensors, such as switches of keyboards and mice.
1 . A deglitch circuit coupled between a signal producing node and a signal processing node, the deglitch circuit comprising:
a delay block coupled to receive a data signal from the signal producing node and to produce a delay data signal;
a first logic gate having a first gate input, a second gate input, and a first gate output, the first gate input being coupled to receive the data signal from the signal producing node and the second gate input being coupled to receive the delay data signal from the delay block;
a second logic gate having a third gate input, a fourth gate input, and a second gate output, the third gate input being coupled to receive the data signal from the signal producing node and the fourth gate input being coupled to receive the delay data signal from the delay block; and
an SR latch having a first latch input, a second latch input, and a latch output, the first latch input being coupled to the first gate output and the second latch input being coupled to the second gate output;
wherein the SR latch provides a deglitched data signal based on the data signal via the latch output to the signal processing node for processing.
2 . The deglitch circuit of claim 1 , wherein the first logic gate removes a positive glitch from the data signal and wherein the second logic gate removes a negative glitch from the data signal.
3 . The deglitch circuit of claim 1 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node in a substantial parallel manner.
4 . The deglitch circuit of claim 1 , wherein the second gate input and the fourth gate input are coupled to receive the delay data signal from the delay block in a substantial parallel manner.
5 . The deglitch circuit of claim 1 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node in a substantial parallel manner and wherein the second gate input and the fourth gate input are coupled to receive the delay data signal from the delay block in a substantial parallel manner.
6 . The deglitch circuit of claim 5 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node via a conductive medium comprising a plurality of conductive traces.
7 . The deglitch circuit of claim 1 , wherein the first logic gate comprises an and-gate and wherein the second logic gate comprises a nor-gate.
8 . The deglitch circuit of claim 7 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node in a substantial parallel manner.
9 . The deglitch circuit of claim 7 , wherein the second gate input and the fourth gate input are coupled to receive the delay data signal from the delay block in a substantial parallel manner.
10 . The deglitch circuit of claim 7 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node in a substantial parallel manner and wherein the second gate input and the fourth gate input are coupled to receive the delay data signal from the delay block in a substantial parallel manner.
11 . The deglitch circuit of claim 7 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node via a conductive medium comprising one of a conductive trace and a wire.
12 . The deglitch circuit of claim 11 , wherein the delay block, the and-gate, the nor-gate, and the SR-latch are parts of an application specific integrated circuits (ASIC) chip.
13 . The deglitch circuit of claim 11 , wherein the data signal is provided from the signal producing node through the delay block, the and-gate, the nor-gate, and the SR-latch to the signal processor using hardwire means.
14 . The deglitch circuit of claim 1 , wherein the delay block, the first gate input, and the third gate input are coupled to receive the data signal from the signal producing node via a plurality of conductive traces and wherein the delay block, the first logic gate, the second logic gate, and the SR-latch are parts of an application specific integrated circuits (ASIC) chip.
15 . The deglitch circuit of claim 14 , wherein the data signal is provided from the signal producing node through the ASIC chip to the signal processor using hardwire means.
16 . A method of deglitching a data signal using a digital logic circuit, the method comprising:
receiving a data signal;
delaying the data signal for a predetermined period to produce a delay data signal from the received data signal;
providing in a substantially parallel manner the data signal to a first gate input of a first logic gate and a first gate input of a second logic gate;
providing in a substantially parallel manner the delay data signal to a second gate input of the first logic gate and the second gate input of the second logic gate;
coupling an SR latch to an output of the first logic gate and an output of the second logic gate; and
providing a deglitched data signal based on the data signal from the SR latch.
17 . The method of claim 16 , wherein the first logic gate removes a positive glitch from the data signal and wherein the second logic gate removes a negative glitch from the data signal.
18 . The method of claim 16 , wherein the receiving the data signal comprises receiving the data signal from a signal producing node via a plurality of conductive traces.
19 . The method of claim 16 , wherein the first logic gate comprises an and-gate and wherein the second logic gate comprises a nor-gate.
20 . The method of claim 16 , wherein the delaying the data signal for the predetermined period comprises:
deciding a size of a glitch to be removed;
providing a decided size large enough so that an SR latch timing constraint of the SR latch is met; and
setting a delay block to the decided size.
21 . A deglitch circuit coupled between a signal producing node and a signal processing node, the deglitch circuit comprising:
first means for receiving a data signal;
second means for delaying the data signal for a predetermined period to produce a delay data signal from the data signal;
third means for receiving the data signal and the delay data signal and for logically removing a positive glitch from the data signal;
fourth means for receiving the data signal and the delay data signal and for logically removing a negative glitch from the data signal; and
fifth means for logically producing a deglitched data signal from the data signal, the fifth being coupled to the third means and the fourth means.
22 . The deglitch circuit of claim 21 , wherein the third means comprises an and-gate, wherein the fourth means comprises a nor-gate, and wherein the fifth means comprises an SR latch.
23 . The deglitch circuit of claim 21 , wherein the second means comprises a delay block for setting a glitch size.