Semiconductor memory device

1. A semiconductor memory device comprising:

a memory cell; and

a first circuit configured to generate a write pulse based on a write command and supply a write current to the memory cell in accordance with the write pulse,

wherein:

the first circuit supplies the write current to the memory cell during a first period when the first circuit receives a first write command,

the first circuit extends the first period during which the write current is supplied to the memory cell when the first circuit receives a second write command within a first time after reception of the first write command, and

an address and write data that are input accompanying the second write command are identical to an address and write data that are input accompanying the first write command.

2. The semiconductor memory device according to claim 1 , wherein the first time is shorter than a time corresponding to a pulse width of a first write pulse which is generated when the first circuit receives the first write command.

3. The semiconductor memory device according to claim 1 , further comprising a controller configured to issue the first write command and to issue the second write command within the first time after issue of the first write command.

4. The semiconductor memory device according to claim 1 , wherein a first write pulse is asserted in response to a first signal generated based on the first write command, and the first write pulse is negated in response to a second signal generated based on the second write command.

5. The semiconductor memory device according to claim 4 , wherein:

the first signal is a delayed signal of a signal generated in response to input of the first write command, and

the second signal is a delayed signal of a signal generated in response to input of the second write command.

6. The semiconductor memory device according to claim 1 , wherein a pulse width of a first write pulse is varied in accordance with a first command if the first command is input to the first circuit after input of the first write command and before input of the second write command.

7. The semiconductor memory device according to claim 1 , wherein the memory cell includes a variable resistance element.

8. A semiconductor memory device comprising:

a memory cell; and

a first circuit configured to generate a write pulse based on a write command and supply a write current to the memory cell in accordance with the write pulse,

wherein:

the first circuit supplies the write current to the memory cell during a first period when the first circuit receives a first write command,

the first circuit extends the first period during which the write current is supplied to the memory cell when the first circuit receives a second write command within a first time after reception of the first write command, and

first write data that is input accompanying the first write command is stored in a buffer, and the buffer is configured to retain the first write data if second write data is input accompanying the second write command.

9. A semiconductor memory device comprising:

a memory cell; and

a first circuit configured to generate a write pulse based on a write command and supply a write current to the memory cell in accordance with the write pulse,

wherein:

the first circuit supplies the write current to the memory cell during a first period when the first circuit receives a first write command,

the first circuit extends the first period during which the write current is supplied to the memory cell when the first circuit receives a second write command within a first time after reception of the first write command, and

the first circuit comprises:

a decoder which decodes the first and second write commands, and selects the memory cell as a memory cell for which a write operation is to be performed;

a circuit which generates a write signal based on the first and second write commands;

a pulse generator which generates first and second write pulses based on the write signal; and

a current supply circuit which keeps supplying the write current to the memory cell for a length of time corresponding to the write pulse.