EEprom writing

It's the nature of the beast. If you can't stand the delay (perhaps because you have other devices on the shared I2C bus(, either implement a second I2C bus (or other dedicated bus such as SPI or Microwire for the EEPROM) or use a nonvolatile technology with less inherent write time, such as ferroelectric RAM or battery-backed SRAM.

Best regards, Spehro Pefhany

I use the I2C bus for writing/reding eeprom 24Cxx, with 8051 Micro family.

When i write to it, i have to wait a lot of time, otherwise nothing is written.

It seems i follow the correct signals sequence, but i cannot get out of this delay.

Is there someone that has experience ?

Enzo

Well, writing an EEPROM takes a few ms per adress. You could do something else in the remaining time. Do you poll for a flag or is there an interrupt ?

Rene

Also, the delay is the same to write one byte, as to write a 'block'. Most of the chips support 16 byte or more 'block write' mode, so you can save a lot of time if moving big amounts of data, by using the block write feature. You can also verify whether the write has finished by doing a 'start', sending a command, and checking for ack. This allows the delay to reduce in some cirumstances (the write time changes with temperature, voltage etc.). The FRAMs are great though. I have used these for a couple of years on various projects, and they are a godsend where you don't want the delays.

Best Wishes

Ramtron has FRAM which has "no delay writes" (actuall 72nS I think).

The have are mostly drop in I2c compatable with 24cxx eerpoms... part no FM24Cxx.

this

So do I. :-)

Please define 'a lot of time'.

Did you code your own routine to handle the I2C bus or use a library routine such as supplied with a compiler ? Are you using an 8051 derivative with a dedicated I2C controller or simply using general port pins ?

Are you using a high level alnguage - if so - which one ? Do your Eeprom writes and reads work OK ?

Well, Eeproms aren't hugely fast ! Maybe you're expecting too much ?

How many bytes of data are you typically writing at a time ?

Graham

What's the data rate on the serial data line to achieve that ? ;-)

That's the blink of an eye to an 8051.

Graham

That's a crazy length of time. Sounds more like a WDT timeout while waiting for a ACK that never comes. Don't quote me on this, but IIRC, you have to poll the device to get it to ACK after a write.

Yes. I've seen enough errors in this kind of routine, even from manufacturers, that I carefully analyze it before using it. Saves a lot of time and understanding the code is never a bad thing.

Best regards, Spehro Pefhany

I'm using general purpose pins of 8051, for SDA and SCL signals. The problem comes from the ACK from the eeprom, that sometimes takes a lot of time to arrive. The SDA pin gooes low after a lot of time (0.5 sec !!!).

The software is in c (IIAR compiler)

I'm doing something wrong.

Enzo

Bingo! I think you start to do another write and see if you get ACK - this means its done with the last one. If not, then do another...

Thanks for mentioning! I was looking for serial SPI compatible RAM for some time.