INITIATION OF FUSE SENSING CIRCUITRY AND STORAGE OF SENSED FUSE STATUS INFORMATION
An integrated circuit includes at least one circuit trimming fuse. A fuse sensor circuit is connected to the trimming fuse and operates in response to a fuse sensing initiation signal to initiate sensing of a state of the trimming fuse and generate an output indicative of the sensed state. A latch circuit, including multiple latch locations, redundantly latches the output indicative of the sensed state. A majority logic state in the latch locations is determined by a polling circuit coupled to the multiple latch locations. The polling circuit outputs that majority logic state as a fuse state output indicative of the sensed state of the fuse. A register in the integrated circuit is loadable with a value. A comparison circuit compares the loaded value in the register to a correct fuseword value and, if there is a match, generates the fuse sensing initiation signal for application to the fuse sensor circuit.
1 . A circuit, comprising:
a trimming fuse;
a fuse sensor circuit connected to the trimming fuse which operates in response to a fuse sensing initiation signal to initiate sensing of a state of the trimming fuse and generate an output indicative of the sensed state;
a data register which is loadable with a value; and
a comparison circuit which compares the loaded value in the register to a correct fuseword value and, if there is a match, generates the fuse sensing initiation signal for application to the fuse sensor circuit.
2 . The circuit of claim 1 wherein the circuit is an integrated circuit.
3 . The circuit of claim 1 wherein the comparison circuit is a combinational logic circuit.
4 . The circuit of claim 1 further comprising a second comparison circuit which compares the loaded value in the register to a correct password value and, if there is a match, generates a pass control signal authorizing operation of the circuit.
5 . The circuit of claim 1 further comprising a latch circuit for latching the output from the fuse sensor circuit indicative of the sensed state of the fuse.
6 . The circuit of claim 5 wherein the latch circuit includes a latch control input, the fuse sensor circuit further generating a latch control signal for application to the latch control input when the output indicative of the sensed state of the fuse is generated.
7 . The circuit of claim 5 wherein the latch circuit comprises a redundant latch including a plurality of individual latches which each latch the output from the fuse sensor circuit indicative of the sensed state of the fuse.
8 . The circuit of claim 7 further comprising a polling circuit coupled to outputs of the plurality of individual latches, the polling circuit operating to determine a majority logic state of the latched outputs from the fuse sensor circuit indicative of the sensed state of the fuse and output that majority logic state as a fuse state output.
9 . The circuit of claim 8 wherein the polling circuit comprises a combinational logic circuit.
10 . The circuit of claim 7 wherein each of the plurality of individual latches includes a latch control input, the fuse sensor circuit further generating a latch control signal for application to each latch control input when the output indicative of the sensed state of the fuse is generated.
11 . The circuit of claim 7 wherein each of the plurality of individual latches includes a latch control input, further comprising a latch control circuit which responds to an indication received from the fuse sensor circuit that the output indicative of the sensed state of the fuse is available and independently generates a separate latch control signal for application to each latch control input.
12 . The circuit of claim 1 wherein the fuse sensing initiation signal is a pulsed signal, the comparison circuit further comprising a pulse generator circuit responsive to the match between the loaded value in the register and the correct fuseword.
13 . A method, comprising:
comparing a loaded fuseword value to a correct fuseword value;
if there is a match, generating a fuse sensing initiation signal; and
performing a fuse sensing operation in response to the generated fuse sensing initiation signal to sense a state of a trimming fuse and generate an output indicative of the sensed state.
14 . The method of claim 13 further comprising latching the output indicative of the sensed state of the fuse.
15 . The method of claim 14 wherein latching comprises redundantly latching the output indicative of the sensed state of the fuse in a plurality of locations.
16 . The method of claim 15 further comprising:
polling the plurality of locations to determine a majority logic state of the latched outputs indicative of the sensed state of the fuse; and
outputting that majority logic state as a fuse state output.
17 . A circuit, comprises:
a trimming fuse;
a fuse sensor circuit connected to the trimming fuse which operates in response to a fuse sensing initiation signal to initiate sensing of a state of the trimming fuse and generate an output indicative of the sensed state;
a register which is loadable with a value;
a first comparison circuit which compares the loaded value in the register to a correct fuseword value and, if there is a match, generates the fuse sensing initiation signal for application to the fuse sensor circuit; and
a second comparison circuit which compares the loaded value in the register to a correct password value and, if there is a match, generates a pass control signal authorizing operation of the circuit.
18 . The circuit of claim 17 wherein the circuit is an integrated circuit.
19 . The circuit of claim 17 further comprising a latch circuit for latching the output from the fuse sensor circuit indicative of the sensed state of the fuse.
20 . The circuit of claim 19 wherein the latch circuit comprises a redundant latch including a plurality of individual latches which each latch the output from the fuse sensor circuit indicative of the sensed state of the fuse.
21 . The circuit of claim 20 further comprising a polling circuit coupled to outputs of the plurality of individual latches, the polling circuit operating to determine a majority logic state of the latched outputs from the fuse sensor circuit indicative of the sensed state of the fuse and output that majority logic state as a fuse state output.
22 . The circuit of claim 17 wherein the fuse sensing initiation signal is a pulsed signal, the first comparison circuit further comprising a pulse generator circuit responsive to the match between the loaded value in the register and the correct fuseword.
23 . A circuit, comprising:
a trimming fuse;
a fuse sensor circuit connected to the trimming fuse which operates in response to a fuse sensing initiation signal to initiate sensing of a state of the trimming fuse and generate an output indicative of the sensed state;
a latch circuit including multiple latch locations to redundantly latch the output indicative of the sensed state;
a polling circuit coupled to the multiple latch location, the polling circuit operating to determine a majority logic state in the latch locations and output that majority logic state as a fuse state output indicative of the sensed state of the fuse;
a register which is loadable with a value; and
a comparison circuit which compares the loaded value in the register to a correct fuseword value and, if there is a match, generates the fuse sensing initiation signal for application to the fuse sensor circuit.
24 . The circuit of claim 23 wherein the circuit is an integrated circuit.
25 . The circuit of claim 23 wherein the fuse sensing initiation signal is a pulsed signal, the comparison circuit further comprising a pulse generator circuit responsive to the match between the loaded value in the register and the correct fuseword.