System for detecting a reset condition in an electronic circuit
View Patent ↗There is disclosed a system for detecting the assertion of a reset signal. A plurality of circuit elements is configurable by a reset signal to output a string of data values in a predetermined pattern. A comparator receives the string of data values and determines whether the string of data values matches the predetermined pattern. If so, the comparator generates an output signal indicative of a reset. In one embodiment, the output signal of the comparator can be used to automatically trigger a reset if the reset signal has not been asserted.
1. A system for detecting the assertion of a reset signal, said system comprising:
(a) a plurality of circuit elements, including an output, configurable by said reset signal to generate a string of data values at said output; and
(b) a comparator, including an input, said input for receiving said string of data values and determining whether said string of data values matches a predetermined pattern;
said comparator generating a confirmatory signal, indicative of attainment of a reset condition, if said string of data values matches said predetermined pattern.
2. The system of claim 1 further comprising logic elements interposed between said output of said plurality of circuit elements and said input of said comparator, said logic elements for modifying said string of data values to produce, at said input of the comparator, a set of signals, each signal of said set having a common digital value when said reset condition is attained.
3. The system of claim 2 wherein said comparator comprises a single logic gate for receiving said set of signals at said input and producing said confirmatory signal.
4. The system of claim 3 further comprising a second logic gate for receiving, as an input, said confirmatory signal and said reset signal, said second logic gate generating an initiation signal to initiate said reset signal in the absence of said confirmatory signal.
5. The system of claim 4 wherein said system is within an integrated circuit and said reset signal provides a system-wide reset of said integrated circuit.
6. The system of claim 2 wherein said plurality of circuit elements comprises flip flops.
7. The system of claim 1 wherein said plurality of circuit elements comprises volatile memory, and wherein said predetermined pattern is stored in non-volatile memory accessible by said comparator.
8. The system of claim 7 further comprising a logic gate to receive said confirmatory signal indicative of attainment of a reset and said reset signal, and to output an initiation signal to control initiation of said reset signal, wherein said logic gate acts to assert said reset signal in the absence of said confirmatory signal indicative of attainment of a reset.