Semiconductor memory device and method of controlling semiconductor memory device
View Patent ↗A semiconductor memory device has a nonvolatile memory cell to which data writing operation is limited to a predetermined logic value. In the case of rewriting data “10101010” written in a first memory core to data “01010101”, since the data writing operation includes writing of a logic value “1” opposite to the predetermined logic value, an erasing operation is needed and the data writing is regulated. By rewriting a pointer value stored in a pointer memory in place of performing the erasing operation, an operation of switching a memory core to be selected to a second memory core (data “11111111”) is performed. Data is newly written into the second memory core selected by the rewritten pointer value.
1. A method of controlling a semiconductor memory device having plural memory cores each having nonvolatile memory cells in which data writing is regulated to a predetermined logic value, comprising the steps of,
at the time of selecting a setting value for setting an internal state from plural candidate values in a predetermined range,
preliminarily writing the plural candidate values in the plural memory cores, and
selecting the memory cores in an irreversible predetermined order and performing a reading operation on the selected memory core.
2. The method of controlling a semiconductor memory device according to claim 1 ,
wherein the device comprises the plural memory cores in which the same candidate value is written as at least one of the candidate values, and the method comprises:
a condition providing step of selecting the memory cores holding the candidate values different from each other in the irreversible predetermined order and conducting a test on the basis of the candidate value; and
a setting step of selecting the memory core having the same value as any one of the candidate values selected according to a result of the test and using the candidate value as the setting value.