Method and apparatus for verifying erasure of memory blocks within a non-volatile memory structure

A computer system comprising:

• a non-volatile memory device for storing digital information organized in sectors, each sector having a data field and a corresponding extension field;
• and
• a controller device for performing reading, writing and erasing operations on a selected plurality of sectors and for further verifying successful erasure of the selected erased sectors, said controller device further including,
• an error detection circuit for detecting errors within each of the sector data field using the corresponding sector extension fields,
• a flash interface circuit coupled to the non-volatile device through a bus including a data bus for receiving an erased sector of information from the non-volatile device through the data bus and operative to pass the data field of the erased sector information and a predetermined extension field to the error detection circuit,
• wherein said error detection circuit calculates an extension field corresponding to the erased sector data field, compares the calculated extension field to the predetermined extension field and upon the calculated extension field not being equal to the predetermined extension field, detects an error in the erased sector.

In a digital system having a non-volatile memory device for storing digital information organized in sectors, each sector having a data field and a corresponding extension field, a controller device for performing reading, writing and erasing operations on a selected plurality of sectors and having an error detection circuit for detecting errors within each of the sector data fields using the corresponding sector extension field, a method for verifying successful erasure of the selected erased sectors comprising:

• receiving an erased sector of information from the non-volatile device through a data bus;
• providing the data field of the erased sector to the error detection circuit;
• providing a predetermined extension field in place of the extension field of the erased sector to the error detection circuit;
• calculating a new extension field corresponding to the erased sector data field;
• comparing the calculated extension field to the predetermined extension field;
• and
• upon the calculated extension field not matching the predetermined extension field, detecting an error in the erased sector.

A method of verifying whether at least a portion of an erased sector of digital information, at lease a portion of a sector previously stored in a non-volatile memory and later erased, has been successfully erased, comprising:

• receiving said at least a portion of an erased sector of information from the non-volatile memory;
• generating an extension code from said at least a portion of an erased sector of information;
• and
• determining whether said portion of said sector has been successfully erased using said extension code with a predetermined code.