Title: Maintaining Data Integrity in EEPROM
1Maintaining Data Integrity in EEPROMs
- Ed Patnaude
- Maxwell Technologies
- San Diego, Ca
2Contents
- EEPROM Technology
- Sources of Data Corruption
- Maintaining Data Integrity
- Summary
3EEPROM Technology
- Most EEPROMs utilize some variation of the
- Floating Gate Technology
A positively charged gate is read as a logic 0.
4Sources of Data Corruption
- Software Errors
- Insufficient Hardware Protection
-
- Programming Issues
5Sources of Data Corruption
- Software Errors
- Inadvertent Writes
- Improper Timing / Buss Contention
- Programming Across Page Boundaries
6Sources of Data Corruption
- Insufficient Hardware Protection
- Uncontrolled Power On/Off
- Uncontrolled Inputs
- Excessive Power Supply Noise
- Data Buss Contention
- No Hardware Write Protection Implemented
7Sources of Data Corruption
- Programming Issues
- Setting Write Protect, or Reset, active during a
write cycle will halt programming resulting in
corrupt data. - Insufficient supply voltage, during a program
cycle, can result in incorrect data being
stored. - Exceeding the manufactures write cycle endurance
specification can cause permanent damage to the
memory cells leaving them un-programmable.
8Maintaining Data Integrity
- Hardware Protection
- Software Protection
- Proper Power Cycling
- Error Detection and Correction (EDAC)
- Power Supply Supervisory Circuitry
- Contingency Plan
9Maintaining Data Integrity
- Hardware Protection
- Most EEPROMs have a RESET or Write Protect
input, when set active, all erase/writes
operations are blocked.
10Maintaining Data Integrity
- Software Data Protection (SDP)
- SDP locks the memory preventing unintentional
erase/writes from occurring. - Normally implemented using the JEDEC Standard
Algorithm - SDP will only protect the memory contents when
the supply voltage is within the normal operating
range.
11Maintaining Data Integrity
- Proper Power Cycling
- Allow Vcc to reach proper operating level before
initiating any Reads or Writes to the EEPROM. - Enable the EEPROM Hardware Write Protection, or
Reset, prior to power down. - Do not remove power while a write cycle is in
process.
12Maintaining Data Integrity
- Error Detection and Protection
- Parity Bits
- Checksum
- Cyclic Redundancy Code
- Error Correction Codes
- Hamming Code
- Reed-Solomon
13Maintaining Data Integrity
- Power Supervisory Circuitry
- Monitor Supply Voltages and provide a RESET
signal - when the voltage drops below a pre-described level
14Maintaining Data Integrity
- Have a Contingency Plan
- Always verify data after a program cycle to
assure an error has not occurred and re-program
if necessary. - Data retention time can be increased by
periodically rewriting the data to the EEPROM. - Have the ability to relocate bad data bytes.
- Use Redundancy if at all possible.
15Summary
- A robust hardware and software design, along
with a contingency plan should corruption occur,
can greatly minimize the risk of system failure
due to data corruption in a EEPROM.