AN2540 - Application note

Implementing the EEPROM emulation

13/25

The procedure of updating a variable entry in the EEPROM is shown in Figure 4.

Figure 4.

If the data to be written is equal to 0xFFFF, it is necessary to find the last data equal to

0xFFFF and to write 0x0000 into the next location to indicate that 0xFFFF represents data

and not a blank location. If the data to be written is different from 0xFFFF, it is then written to

the last location that contains 0xFFFFh (the following location should not contain 0x0000).

This function returns 0 on success, VARIABLE_FULL if there is not enough memory space

for a variable update, or a Flash error code indicating an operation failure (erase or

program).

Table 6.

WriteVerifyVariableFull

Function Name

WriteVerifyVariableFull

Behavior

Description

If a write operation takes place, the write process must either update a variable,

or create the first instance of a variable.

Input Parameter

– variable index, in the demonstration example provided: (0 for A, 1 for B or 2

for C).

– T: variable Array

– 16-bit data to be written

Return Parameter

Returns 1 on success or 0x80 if variable is full or Flash error code

Called functions

FindValidSector,FMI_ReadWord,FMI_WriteHalfWord

Add element request

full

current record

Add new element at

the 1st empty element

place in the current

record of active sector

Erase previous active sector

End

End

Change the active sector

Find Valid sector

Yes

No

FindValidSector()

WriteVerifyVariableFull()

Copy each latest element of

each available record by

reading from bottom taking

into account the new

updated element.

EepromSectorTransfer()

ReadVariable()

Function call

ai14088