STM8S207MBT3B datasheet(15/103 Pages) STMICROELECTRONICS

15 / 103 page

STM8S207xx, STM8S208xx

Product overview

Doc ID 14733 Rev 9

15/103

4.4

Flash program and data EEPROM memory

●

Up to 128 Kbytes of high density Flash program single voltage Flash memory

●

Up to 2K bytes true data EEPROM

●

Read while write: Writing in data memory possible while executing code in program

memory.

●

User option byte area

Write protection (WP)

Write protection of Flash program memory and data EEPROM is provided to avoid

unintentional overwriting of memory that could result from a user software malfunction.

There are two levels of write protection. The first level is known as MASS (memory access

security system). MASS is always enabled and protects the main Flash program memory,

data EEPROM and option bytes.

To perform in-application programming (IAP), this write protection can be removed by writing

a MASS key sequence in a control register. This allows the application to write to data

EEPROM, modify the contents of main program memory or the device option bytes.

A second level of write protection, can be enabled to further protect a specific area of

memory known as UBC (user boot code). Refer to Figure 2.

The size of the UBC is programmable through the UBC option byte (Table 13.), in

increments of 1 page (512 bytes) by programming the UBC option byte in ICP mode.

This divides the program memory into two areas:

●

Main program memory: Up to 128 Kbytes minus UBC

●

User-specific boot code (UBC): Configurable up to 128 Kbytes

The UBC area remains write-protected during in-application programming. This means that

the MASS keys do not unlock the UBC area. It protects the memory used to store the boot

program, specific code libraries, reset and interrupt vectors, the reset routine and usually the

IAP and communication routines.

Figure 2.

Flash memory organisation

Programmable area from 1 Kbyte

Data

UBC area

Program memory area

Data memory area (2 Kbytes)

(2 first pages) up to 128 Kbytes

EEPROM

Remains write protected during IAP

memory

128 Kbytes

Flash

Up to

Write access possible for IAP

program

memory

(1 page steps)

Option bytes

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