ATMEL Cryptomemory USART EEPROM AT88SC

[vonsproken]

Hi,

Here are two data sheets,

http://www.atmel.com/Images/Atmel-2021S-CryptoMem-AT88SC0104C-Datasheet-Summary.pdf
http://www.atmel.com/images/Atmel-5211-CryptoMem-Full-Specification-Datasheet.pdf

The first datasheet is the EEPROM chips itself, so from this each byte will take 5ms to write, however there is the capability of a page write of 16 byte. I would have assumed from this datasheet that I could write 16 bytes in 5ms, the datasheet is unclear to the protocol of reading and writing to the chip.

The second datasheet goes into detail of the range, the commands of how to read / write and the memory structure of the ranges. So here is my confusion. There is an acknowledge bit after each 8-bit word (page 31), scroll down to page 32 and It tells you the delay before the next command. I would have assumed that the page write would take 5ms but after reading this It would take more like 100ms. To write the whole chip would take 800ms and this is a small 128byte chip, how long would a larger chip take? I know I can use the anti-tearing feature to write however this is limited to 8 byte, it would still take 20ms to write.

Am I missing something in the datasheet, should writing really take this long?

Thanks,
John

 

[Ian Rogers]

It's only 5ms at 25°... You have to allow 7ms.... One page at a time... the write cycle only kicks in after your stop command when in write mode... So 16bytes takes 7ms

If you poll the acknowledge flag you may get as little as 1mS write cycle.

 

[vonsproken]

Thanks for the reply,

That's good news for me, I have re-read the datasheet over and over but clearly misread the acknowledge flag. Reading other EEPROM chips datasheets I understood that a page of data could be sent and then it was only written after the stop bit, what confused me was the acknowledge bit between each word, then the next table in the datasheet stating how long delay an acknowledge delay was.

So from what I understand is that the acknowledge flag needs to be polled after every word to check that the next word can be sent. After writing a page / command (ending with a stop bit) the EEPROM will start to write taking between 5 - 10ms depending on temperature, the next command acknowledge flag will only clear when the EEPROM has completed writing, once complete more data can be received by the EEPROM chip.