Semiconductor memory

A semiconductor memory comprising:

• a first electrically rewritable non-volatile semiconductor memory;
• a volatile cache semiconductor memory whose capacity is equal to or less than a capacity of said first non-volatile semiconductor memory and which is used to temporarily hold data to be written into the non-volatile semiconductor memory;
• a data control circuit for writing data from a processor unit connected to said data control circuit into said cache semiconductor memory, for reading out the data from the non-volatile semiconductor memory and the volatile cache semiconductor memory, and for transferring the data from the volatile cache semiconductor memory to the non-volatile semiconductor memory;
• a redundant electrically rewritable non-volatile semiconductor memory for providing storage of data normally stored in said first non-volatile semiconductor memory when said first non-volatile semiconductor memory is defective;
• and
• a battery to hold the data in the volatile cache semiconductor memory when a power supply for the semiconductor memory is shut off;
• wherein said data control circuit comprises:
• a second non-volatile memory to store a block bit map table corresponding to a block of a flash EEPROM (electrically erasable programmable read-only memory) which comprises said first non-volatile semiconductor memory;
• and
• a third non-volatile memory to store an alternate address when said first non-volatile memory is defective;
• wherein said redundant electrically rewritable non-volatile semiconductor memory comprises a redundant flash EEPROM.