STM8AF5178 datasheet(17/110 Pages) STMICROELECTRONICS

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STM8AF52/62xx, STM8AF51/61xx

Product overview

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5.4.2

Write protection (WP)

Write protection in application mode is intended to avoid unintentional overwriting of the

memory. The write protection can be removed temporarily by executing a specific sequence

in the user software.

5.4.3

Protection of user boot code (UBC)

If the user chooses to update the Flash program memory using a specific boot code to

perform in application programming (IAP), this boot code needs to be protected against

unwanted modification.

In the STM8A a memory area of up to 128 Kbytes can be protected from overwriting at user

option level. Other than the standard write protection, the UBC protection can exclusively be

modified via the debug interface, the user software cannot modify the UBC protection status.

The UBC memory area contains the reset and interrupt vectors and its size can be adjusted

in increments of 512 bytes by programming the UBC and NUBC option bytes

(see Section 9: Option bytes on page 51).

Figure 2.

Flash memory organization of STM8A products

5.4.4

Read-out protection (ROP)

The STM8A provides a read-out protection of the code and data memory which can be

activated by an option byte setting (see the ROP option byte in section 10).

The read-out protection prevents reading and writing Flash program memory, data memory

and option bytes via the debug module and SWIM interface. This protection is active in all

device operation modes. Any attempt to remove the protection by overwriting the ROP

option byte triggers a global erase of the program and data memory.

The ROP circuit may provide a temporary access for debugging or failure analysis. The

temporary read access is protected by a user defined, 8-byte keyword stored in the option

byte area. This keyword must be entered via the SWIM interface to temporarily unlock the

device.

Programmable area from 1 Kbyte

Data

UBC area

Program memory area

Data memory area

(first two pages) up to program memory

EEPROM

Remains write protected during IAP

memory

Write access possible for IAP

Option bytes

end - maximum 128 Kbytes

Flash

program

memory

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