Artificial neuron apparatus

1. An artificial neuron apparatus comprising a resistive memory cell connected in circuitry having:

a first input terminal for applying neuron input signals, each comprising a read portion and a write portion, to the memory cell;

a read circuit for producing a read signal dependent on resistance of the memory cell;

an output terminal for providing a neuron output signal dependent on the read signal in a first state, being one of a low-resistance state and a high-resistance state, of the memory cell;

a storage circuit for storing a measurement signal, the measurement signal being based on the resistance of the memory cell and dependent on the read signal; and

a switch set operable to supply the read signal to the storage circuit during application of the read portion of each neuron input signal to the memory cell, and, after application of the read portion, to apply the measurement signal in the apparatus to enable resetting of the memory cell from said first state to a second state, being the other of said low-resistance and high-resistance states;

wherein the apparatus is adapted such that resistance of the memory cell is progressively changed from said second state to said first state by application of the write portions of successive neuron input signals to the cell;

wherein said first state is said low-resistance state, the apparatus being adapted such that resistance of the memory cell is progressively reduced by application of the write portions of successive neuron input signals to the cell;

wherein each neuron input signal includes a reset portion after the read portion thereof, the apparatus including a second input terminal for receiving, during the reset portion of each neuron input signal, a reset signal for resetting the memory cell from said low-resistance state to said high-resistance state, and wherein the switch set includes:

a first switch, operable in response to the measurement signal in said low-resistance state of the memory cell, to connect the second input terminal to the memory cell; and

a second switch, operable in response to application of the reset signal at the second input terminal, to apply the measurement signal to the first switch.

2. The apparatus as claimed in claim 1 including a third switch, operable in response to the read portion of a neuron input signal, to supply the read signal to the storage circuit during application of that read portion to the memory cell.

3. The apparatus as claimed in claim 1 wherein the read circuit comprises a read resistance connected between the memory cell and a reference terminal.

4. The apparatus as claimed in claim 3 wherein:

the apparatus includes a fourth switch connected between the memory cell and said reference terminal, the fourth switch being operable, in response to each of said reset signal and the write portion of each neuron input signal, to short the read resistance.

5. The apparatus as claimed in claim 4 wherein the output terminal is connected to the read circuit whereby the neuron output signal comprises the read signal in said low-resistance state of the memory cell.

6. The apparatus as claimed in claim 5 wherein the memory cell comprises a phase-change memory cell.

7. An artificial neuron apparatus comprising a resistive memory cell connected in circuitry having:

a first input terminal for applying neuron input signals, each comprising a read portion and a write portion, to the memory cell;

a read circuit for producing a read signal dependent on resistance of the memory cell;

an output terminal for providing a neuron output signal dependent on the read signal in a first state, being one of a low-resistance state and a high-resistance state, of the memory cell;

a storage circuit for storing a measurement signal, the measurement signal being based on the resistance of the memory cell and dependent on the read signal; and

a switch set operable to supply the read signal to the storage circuit during application of the read portion of each neuron input signal to the memory cell, and, after application of the read portion, to apply the measurement signal in the apparatus to enable resetting of the memory cell from said first state to a second state, being the other of said low-resistance and high-resistance states;

wherein the apparatus is adapted such that resistance of the memory cell is progressively changed from said second state to said first state by application of the write portions of successive neuron input signals to the cell;

wherein each neuron input signal includes a reset portion after the read portion thereof, and wherein:

the apparatus includes a second input terminal for receiving, during the reset portion of each neuron input signal, a reset signal for resetting the memory cell from said first state to said second state;

the apparatus includes an output circuit comprising a comparator for producing a control signal in response to the measurement signal in said first state of the memory cell, and a signal generator for supplying the neuron output signal to the output terminal in response to said control signal;

the switch set includes a first switch, operable in response to the read portion of a neuron input signal, to supply the read signal to the storage circuit during application of that read portion to the memory cell;

the switch set includes a second switch, operable in response to the reset portion of a neuron input signal, to supply the measurement signal to the output circuit during application of that reset portion to the memory cell; and

the switch set includes a third switch, operable in response to said control signal, to connect the second input terminal to the memory cell.

8. The apparatus as claimed in claim 7 wherein said first state is said low-resistance state and wherein the read circuit comprises a read resistance connected between the memory cell and a reference terminal.

9. The apparatus as claimed in claim 7 wherein the memory cell comprises a phase-change memory cell.