Multi-state non-volatile flash memory capable of being its own two state write cache

A method of operating a flash EEPROM cell array, comprising:

• caching a file of incoming data into a given number of cells of the array according to an amount of data within the file,
• thereafter, reading said data file from the array,
• compressing the read data file by applying a compression algorithm to the read data file that translates the data file into a compressed file, and
• writing the compressed data file into a significantly fewer number of cells of the array than said given number.

A method of operating a flash EEPROM cell array on one or more integrated circuit chips, comprising:

• operating individual cells of at least a portion of the array with either a first number of storage states or a second number of storage states higher than the first number,
• writing an incoming data file into cells of said at least a portion of the array in the first storage state,
• thereafter, reading said data file from the array, and
• rewriting the read data file into said at least a portion of the memory in the second state, thereby to compress storage of the data file into fewer cells of the array, wherein the reading and rewriting of the data file occurs in response to the memory array becoming full with data.

A method of operating a memory system of flash EEPROM cells organized into blocks of cells that are erasable together, wherein the individual cells are operable in any of at least a first data density level of two storage states and a second data density level of more than two storage states, comprising:

• initially writing data into blocks of cells at the first density level,
• determining when a threshold proportion of the memory system blocks are filled with data written into the blocks with the first density level,
• thereafter compressing data already stored in the memory in the first density level by reading said stored data at the first density level from a first number of blocks of cells and rewriting the read data at the second density level into a second number of blocks of cells less than the first number of blocks of cells, thereby to make a number of blocks of cells equal to a difference between said first and second numbers of blocks available to store additional data, and
• thereafter storing additional data in at least some of the number of blocks made available by the data compression.

A method of operating a memory system of flash EEPROM cells organized into blocks of cells that are erasable together, wherein the individual cells are operable in any of at least a first data density level of two storage states and a second data density level of more than two storage states, comprising:

• writing a file of incoming data into the memory system with a first set of memory cell threshold voltage levels,
• thereafter, reading said data file from the memory system,
• rewriting the read data file into the system with a second set of memory cell threshold voltage levels greater than that of said first set, and
• maintaining separate counts for the blocks individually of the number of times that data has been written into the individual blocks with the first set of threshold voltage levels and the number of times with the second set of threshold voltage levels.