PM0051

Programming STM8 Flash microcontrollers

Doc ID 14614 Rev 3

23/27

4.6

Memory access versus programming method

Table 8 gives a description of possible accesses from the core to memory areas according

to the programming method.

Table 8.

Mode

ROP

Memory Area

STM8S and STM8A

Access from core

User, IAP, and

Bootloader (if

available)

Readout protection enabled

Interrupt vectors

User boot code area (UBC)

R/E

Main program

Data EEPROM area (DATA)

Option bytes

R

Readout protection disabled

Interrupt vectors

R/W(2)/E

User boot code area (UBC)

Main program

R/W/E(3)

Data EEPROM area (DATA)

R/W(4)

Option bytes

SWIM active (ICP

mode)

Readout protection enabled

Interrupt vectors

P

User boot code area (UBC)

P

Main program

P

Data EEPROM area (DATA)

P

Option bytes

(7)

Readout protection disabled

Interrupt vectors

R/W(2)/E

User boot code area (UBC)

R/E(5)

Main program

R/W/E(3)

Data EEPROM area (DATA)

R/W(4)

Option bytes

R/W(6)

1.

R/W/E = Read; Write and Execute;

R/E = Read and Execute (write operation forbidden);

R = Read (write and execute operations forbidden);

P = the area cannot be accessed (read, execute and write operations forbidden);

2.

When no UBC area has been defined, the interrupt vectors can be modified in user /IAP mode.

3.

The Flash program memory is write protected (locked) until the correct MASS key is written in the FLASH_PUKR. It is

possible to lock the memory again by resetting the PUL bit in the FLASH_IAPSR register. If wrong keys are provided, the

device must be reset and new keys programmed.

4.

The data memory is write protected (locked) until the correct MASS key is written in the FLASH_DUKR. It is possible to lock

the memory again by resetting the DUL bit in the FLASH_IAPSR register. If wrong keys are provided, another key program

sequence can be performed without resetting the device.

5.

To program the UBC area the application must first clear the UBC option byte.

6.

The option bytes are write protected (locked) until the correct MASS key is written in the FLASH_DUKR (with OPT set to

‘1’). It is possible to lock the memory again by resetting the DUL bit in the IAPSR register. If wrong keys are provided,

another key program sequence can be performed without resetting the device.

7.

When ROP is removed, the whole memory is erased, including the option bytes.