AN4324 datasheet(21/31 Pages) STMICROELECTRONICS

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AN4324

Software

DocID024963 Rev 2.0

21/31

6.1

STC3115 RAM memory organization proposal

The STC3115 device embeds a 16-byte RAM memory area.The registers of this area can

be used to periodically save the battery status. This allows battery information to be

recovered when the application is stopped but the battery is not unplugged.

The STC3115 registers can be initialized with memorized data (see Section 6.2) which is

called "restoration". The choice of whether to use a default initialization or a restoration is

based on the STC3115 CTRL_REG and on the RAM memory content.

A RAM organisation is proposed in Table 6 below. The RAM test word is a fixed word but,

the cyclic redundancy check (CRC) word has to be calculated after each RAM write

operation. The CRC calculation can be made using any standard algorithm.

Before checking if the STC3115 can be restored or not, chcek to see if the RAM data can

be used to initialize the STC3115 registers or not i.e. check if the test and CRC words

located in the RAM memory are used to secure and check the validity of the RAM content.

Table 6: STC3115 RAM stack example, 16 bytes @0x20

RAM register

Content proposal

REG_RAM0

RAM test word

REG_RAM1

Battery SOC_LOW

REG_RAM2

Battery SOC_HIGH

REG_RAM3

Battery CC_CNF_LOW

REG_RAM4

Battery CC_CNF_HIGH

REG_RAM5

Battery VM_CNF_LOW

REG_RAM6

Battery VM_CNF_HIGH

...

REG_RAM15

CRC

16 RAM bytes can be used to save other information/events

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