EEPROM write protect

kolyur

I noticed that the 24LC series EEPROMs can be write protected by pulling pin 7 high. For a commercial product with in-circuit programming capability, is there any reason to make use of the write protect? My thought was to have a dip switch or jumper on the board that could toggle pin 7 from Vss to Vcc after Prop programming is complete. I guess my real question is, are EEPROMs ever susceptible to data loss/corruption or inadvertent writes that could be avoided by using the write protect? Parallax just shows pin 7 grounded on their schematics so they must not think it's necessary.

Any opinions?

Cluso99

Some of my boards have a 10K pullup and a link to gnd (being a WE write enable pin/shunt). Why? Well, some of my users may not have a propplug to reprogram the eeprom. The code in the eeprom is frozen and all it does is boot a binary from the microSD. So, the microSD boot file can be updated by the pc, and no propplug is required.

Mike Green

Serial EEPROMs are not easily written to except by programs specifically designed to write to the EEPROM. It would take several complex errors for a program that just reads from an EEPROM to accidentally write to it. On the other hand, it's easy enough to load the wrong program into RAM by accident and execute it so that the program writes to the unprotected EEPROM. As Cluso99 suggests, it's better to prevent writes to the EEPROM once the EEPROM is properly programmed, particularly if you don't have an easy way to reload the EEPROM properly.

kolyur

Pullup+shunt idea sounds good, I think I'll make use of that. Thanks for the suggestion.

Cluso99

Or if you have the space, a 1x3pin header with the center pin to WP and the other pins to 3v3 and Gnd. Then shift the shunt to either postition.