RG14 datasheet(15/56 Pages) RENESAS

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RL78 Family

Chapter 2

EEPROM Emulation

EEPROM Emulation Library Pack02

R01US0068EJ0100

Rev.1.00

Page 15 of 53

Mar. 28, 2014

2. 3. 5

Structure of Stored Data

The structure of stored data when user data is written to an EEL block is shown in the figure below. A data is

composed of three parts: the start-of-record (SoR) field and the end-of-record (EoR) field and the data field. The

EEL descriptor table can be used to set data for use in the EEL. Each data is referred to by an identification number

(ID) and can have a size between 1 and 255 byte. (The exact specification of the format of the EEL descriptor can

be found in Section 4.3)

Each time data is written, stored data increase in the EEL block and multiple units of stored data exist in the EEL

block, but only the most recent stored data is referenced.

SoR and EoR build up the so-called reference data which is required for the management of the data. The

reference data and user data values are stored in different sections of the active block, namely the reference area

and the data area, respectively. Figure 2-6 shows the overview of the entire structure of stored data.

Figure 2-6

Structure of Stored Data

Table 2-4

Description of Each Field of Data Area

Name

Description

SoR field

(Start of Record)

The one-byte SoR field contains the ID of data. This field indicates the start of write

processing. Data IDs 0x00 and 0xFF are not used to avoid patterns of erased cells.

EoR field

(End of Record)

The one-byte EoR field contains a 0xFF – data ID value.

This field indicates successful end of write processing. If writing does not end normally due

to a device reset or other reasons, the corresponding stored data is ignored by the EEL.

data field

The data field contains the user data. The size of user data is 1 to 255 bytes. When data of

two bytes or more is stored, the smallest address of the data is allocated to the smallest

address of the data field (as shown in figure 2-7)

Data is written to the EEL block in the order of SoR -> data field -> EoR. If write processing does not end

successfully, the immediately previous data becomes valid.

Note1: The total size of the reference consumed by each stored data is 2 bytes. This should be considered when

evaluating the free space in a block before writing the data through the EEL_GetSpace function.

Note2: No checksum is added to user data. If a checksum is needed, add it to user data and check through the

user program.

Data

0xFF -　ID

reference data in EEL

block reference area

SoR

EoR

0x0000

Data Size - 1

data field in EEL

block data area

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