3 Application example: EEPROM emulation using ST10F27x Flash library

AN2244

10/17

ReadVariable( ) routine

This function reads variable data. Only last update is read. The function enters in a loop in

which it reads the variable entries until the last one is found. Finally, the data is returned.

See below for the procedure of reading the last variable entry in the eeprom.

Figure 5.

ReadVariable flowchart

WriteVerifyVariableFull( ) routine

If a write should occur, the write process must either update a variable, or create the first

instance of a variable. The routine has as parameters:

●

variable index (0 for A, 1 for B or 2 for C)

●

all variables Array

●

32-bit data to be written

If the data to be written is equal to 0xFFFFFFFF, we look for the last data equal to

0xFFFFFFFF and we write 0x00000000 in next location to indicate that 0xFFFFFFFF is a

data and not a blank location.

Find Valid sector

Read_Data=0xFFFFFFFF ?

address = base address of the variable in the valid sector

ReadVariable

No

Yes

No

Read_data = FlashRead(address)

FlashRead(address+4) =0x00000000?

FlashRead(address+4) =0xFFFFFFFF?

Yes

address = address + 8

Yes

address = variable start address ?

return VARIABLE_EMPTY

Yes

No

FlashRead(address-8)=0xFFFFFFFF?

&&

FlashRead(address-4)=0x00000000?

No

output = FlashRead(address - 4)

return output

Yes

output = 0xFFFFFFFF

return output

address = address +4