>As my calculations, this memory should have 312,5 KB.
I assume that comma was meant to be a decimal point. When writing in 
english please use english conventions for writing numbers.

 >So, wich memory you indicates to me? Considering this relative number
 >of read/write and that it must be serial

What you would ideally want is a I2C or SPI static ram. The trouble is 
that as far as I can tell noone makes them in a decent capacity. The 
largest i've found so far is 512Kbit and that's from a company i've 
never heard of before and listed as a future product. Microchip have a 
256kbit one ( part number 23K256 ) but that seems to fall far short of 
your requirements.

Ramtrons fram seems to come in higher capacities (up to 2Mbit which 
translates to 256KB ) but it's still too small to meet your requirement 
with a single chip and while it is availible in soic the soic version 
(*FM25H20-G)* seems to be practically unobtainable (other than samples 
and companies that give the distinct impression they are only interested 
in LARGE orders) leaving you with the horrible "DFN" package 
(*FM25H20-DG*) to deal with. It's also expensive.

You don't ideally want an EEPROM or flash chip for this sort of 
application because of the slow writing, limited write cycles and often 
more complex write procedures but it may turn out to be the only way to 
get the capacity at an acceptable price and size. How many rewrites/day 
and what lifetime do you requite.
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