Incremental erasing of flash memory to improve system performance

A method of erasing a page in a system including a CPU, a flash memory including an array of flash memory cells, a flash memory controller coupled to the flash memory and also coupled by a memory bus to the CPU, the method comprising:

• operating the CPU in response to a page erase signal produced during execution by the CPU of a user application program to erase a page of the flash memory by causing the CPU to perform the steps of
• (a) generating a first incremental page erase interval of substantially shorter duration than a total erase time required to erase the flash memory;
• (b) causing the memory controller to take control of the memory bus and apply erase signals to all flash memory cells of the page during the first incremental page erase interval;
• (c) causing the CPU to take control of the memory bus after the first incremental page erase interval and execute a pending interrupt service routine request and/or background task;
• and
• (d) performing steps (a) through (c) for a plurality of additional incremental page erase intervals, respectively, the cumulative amount of erase time of all of the incremental page erase intervals being sufficient to result in erasure of the page with at least a predetermined retention time.

A system comprising:

• (a) a CPU;
• (b) a flash memory including an array of flash memory cells;
• (c) a flash memory controller coupled to the flash memory and also coupled by a memory bus to the CPU,
• (d) means for operating the CPU in response to a page erase signal produced during execution by the CPU of a user application program to erase a page of the flash memory by
• i. generating a first incremental page erase interval of substantially shorter duration than a total erase time required to erase the flash memory,
• ii. causing the memory controller to take control of the memory bus and apply erase signals to all flash memory cells of the page during the first incremental page erase interval,
• iii. causing the CPU to take control of the memory bus after the first incremental page erase interval and execute a pending interrupt service routine request and/or a background task, and
• iv. repeating steps (i) through (iii) for a plurality of additional incremental page erase intervals, respectively, the cumulative amount of erase time of all of the incremental page erase intervals being sufficient to result in erasure of the page with a predetermined retention time.