13/19

EEPROM Emulation with STR71x

Figure 2. Software example concept

In this example a sector is erased only when it is full and the last word on each sector indicates

the status of the corresponding sector:

– 0x600D (Good) indicates a valid sector,

– 0xFFFF (Default value after an erase operation) indicates an invalid sector.

This software implements also a status bit for each Data-set. When a new Data-set is written

to the Data-set area, the software will reset the corresponding bit in the status bits area.

Figure 2. shows an example of a mechanism for setting the status bits in the status bit area.

This figure shows that Data-Set-3 is the valid one because there is three ‘0’s in the status bit

area.

Note: This mechanism takes into account the case when the Data-Set value is 0xFFFFFFFF which is the

default value after an erase operation.

4.2 SOFTWARE OUTPUT FUNCTIONS

There are three output functions in the software as described below.

0xFFFFFFFF

0xFFFFFFFF

0

0

0

Data-set-1

0xFFFFFFFF

STR71x Flash Sector 0

STR71x Flash Sector1

Switch between each sector

(Erase one when full)

Area for Status bits

Area for Data-set storage

valid Flash sector

1

1

1

1

1

1

1

1

1

1

1

1

1

The last “0” corresponds

to the valid Data-set

Data-set-2

Data-set-3

Status bits for

0x600D: Valid sector

0xFFFF: Invalid sector

0xFFFFFFFF

0xFFFFFFFF

0x600D

0xFFFF

0xFFFFFFFF