User Guide

2.2 Page EEPROM strategy 2: data class budget
The second cycling strategy recommends the designer to allocate enough memory for a data class. The memory
allocated is calculated with the total amount of cycles the data class realizes during the whole application lifetime.
If different data class are cycled, several parts of the memory should be allocated for each data class type.
Example:
An application runs with the M95P32 page EEPROM, 32 bytes are cycled every minutes and 4 bytes every 10
minutes. The application lifetime is 10 years.
Two data class can be identified:
• dataClass#1:         
           
• dataClass#2:         
          
As the page cycling endurance of page EEPROM products is 500 k:
dataClass#1 needs at least 11 pages to fit the 5 256 000 cycles (
  
 
), which represents 478 182 cycles per
page
dataClass#2 needs at least 2 pages to fit the 525 600 cycles (
 
 
), which represents 262 800 cycles per
page
The following figures show how these data class can be allocated in a 32 Mbit page EEPROM..
Figure 3. Cycling Strategy with data class budget
DT57098V1
dataClass#2
dataClass#1
Read-only data
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Position 0
Position 10
The cycle begins at pointer position 0. Each cycle, the pointer is incremented to write the next page. When the
last page is reached, the position is reset. So, the 11 pages are cycled 478182 times. This strategy has the
benefit of distributing the cycling over several locations and avoid max stress on a same area.
AN5866
Page EEPROM strategy 2: data class budget
AN5866 - Rev 1
page 5/14