Read/write cycle life of RTC backup registers (STM32F373)

[Tran Viet]

Posted on March 28, 2017 at 09:54

Hi all,

I'am using STM32F373 MCU, in my application,

the 

RTC backup registers

 updated every 10 minutes

.

I know some memory cycles limit read/write cycles, Eg, Eeprom memory only allows 10000 write /read  cycles, if greater than that eeprom will die.

So, I wonder

RTC backup registers

have the same Epprom memory operations? Can I do multiple reads/writes cycle without fear of RTC Backup registers death?

Please confirm for me !

Thank in advance,

Viet Tran

[Uwe Bonnes]

Posted on March 28, 2017 at 14:52

RTC Backup is SRAM, with eventual battery backup. So nearly infinite write cycles.

[Tran Viet]

Posted on March 29, 2017 at 02:37

Thanks Uwe Bonnes,

You can explain the difference in structure between SRAM and Eeprom, why SRAM nearly infinite write cycles but Eeprom ins limited ?

[Tesla DeLorean]

Posted on March 29, 2017 at 04:46

SRAM is an arrangement of transistors that can hold, actively, two distinct states, there is no charge holding structure, and nothing to wear out

https://en.wikipedia.org/wiki/Static_random-access_memory

 

Electrons get trapped in EEPROM over cycles, to the point it can only represent one state, instead of two

https://en.wikipedia.org/wiki/EEPROM

 

Think of EEPROM as a Lead Acid or NiCad battery it has some finite charge cycles, until the nature of the storage cell changes

[waclawek.jan]

Posted on March 29, 2017 at 07:44

RAM is built of standard MOSFET transistors arranged into a flip-flop circuit. You can switch those transistors on and off as many times as you want, without influencing their properties. To retain information in a RAM you need to have a permanent power source, usually a battery backup.

EEPROM is based on a special MOSFET transistor with a floating, i.e. insulated portion of the gate. When programming/erasing, high voltage (generated internally in the IC) is placed to that transistor and then electrons can enter/exit that gate through an extremely thin insulator. Without the high voltage, electrons content in the floating gate does not change thus the transistor retains its on/off state even without permanent power source. However, the programming/erasing process leaves a very small portion of electrons trapped inside the insulator. This gets significant by repeating the programming/erasing process. See for example EEPROM chapter in wikipedia.

JW

[Uwe Bonnes]

Posted on March 29, 2017 at 11:23

Some look in a book about semiconductor physic will help and wikipedia too.