Microchips's EEPROM: how fast?

[Hank Fletcher]

I was wondering if anyone might be able to clue me in to how fast you can fill with data, and/or read the data again from Microchip's EEPROM chips. Sorry for not directly quoting datasheets here, but I seem to remember seeing something to the effect of 2ms wait time for writing, but I wasn't sure how to interpret that.

Surely it couldn't mean 2ms per bit? It'd take a long time to write to an entire 1Mbit chip at that rate! I'm guessing mcu speed is a factor here, so presuming 8MHz, would anyone like to ballpark how long it'd take to write 1Mbit, based on you experience with the 1Mbit chip or similar (maybe the 256Kbit chip)? And how fast I coud read the data again?

Thanks!

 

[ericgibbs]

hi,
I think this would be fast enough.
**broken link removed**

 

[Papabravo]

Rule of thumb is that you can read an EEPROM as fast as the interface, eg. SPI, I2C, or parallel will let you on a byte or word basis.

It takes on the order of milliseconds to write a byte or a word. It used to be 10 milliseconds per byte or word. I could believe 2 milliseconds per byte or word on more modern devices.

The reason for this disparity is the necessity to use a high voltage to transfer charge onto the floating gate of a MOSFET. We all know it takes time to charge a capacitor.

EDIT: yeah - what Eric said.

 

[Mike - K8LH]

If I'm not mistaken (forgive me it's been awhile), I think some of those EEPROM chips have a "page mode" or something similar where the "long write", so to speak, can occur after writing 256 bytes or something like that.

What particular EEPROM chips are you lookin' at Hank?

Mike

 

[Hank Fletcher]

What particular EEPROM chips are you lookin' at Hank?

Maybe some of these?
25xx1024 - 1 Mbit - SPI Serial EEPROM Family - WWW Memory Tree

 

[Pommie]

I've used the I²C version of that chip and a page write (128 bytes) takes 3mS. You can transfer and write a page in 128*10*1/400,000+0.003 = 6.2mS. The whole EEPROM in 1024*0.0062 = 6.4 seconds. The above assumes a 400kHz bus rate. Reading can be done at around 40k byte per second.

Mike.

 

[Hank Fletcher]

The whole EEPROM in 1024*0.0062 = 6.4 seconds.

Sweeeeeet. Thanks!