Programming STM8 Flash microcontrollers

PM0212

16/22

Doc ID 022351 Rev 2

The erase/program cycle lasts longer if the whole word containing the byte to be

programmed is not empty because in this case an erase operation is performed

automatically. If the word is empty, the erase operation is not performed. However, if a

defined programming time is wanted, the FIX bit in the FLASH_CR1 register forces the

programming operation to always erase first whatever the contents of the memory.

Therefore a fixed programming time is guaranteed (erase time + write time).

To erase a byte location, just write ‘0x00’ to the byte location.

Caution:

A byte programming operation performs a word (4-byte) access to the Flash program

memory. If a byte program operation is interrupted by a reset, the 4 bytes programmed in the

memory may be corrupted.

4.5

Programming the option bytes

Option bytes are used to configure the device hardware features as well as the memory

protection. They are stored in a dedicated memory block.

4.5.1

Summary of memory dedicated option bytes

The Flash program memory includes several option bytes dedicated to memory protection:

●

ROP

The ROP option byte is used to prevent the Flash program memory from being read

and modified in ICP/SWIM mode. Refer to Section 3.1: Readout protection for a

detailed description of readout protection.

●

PCODESIZE

The PCODESIZE option byte is used to configure the size of the proprietary code area

(PCODE) which can be used to store proprietary software libraries. The minimum size

of the proprietary code area is of 1 page (64 bytes) and the maximum size of

253 pages. The PCODESIZE option byte can be modified only in ICP/SWIM mode.

Refer to Section 3.2: Proprietary code area protection for a detailed description of the

PCODE area and PCODESIZE option byte.

●

UBC

The UBC option byte is used to program the size of the write protected user boot code

area. The boot area always includes the reset and interrupt vectors and can go up to

the full program memory size. The boot area size granularity is of one page.

Refer to Section 3.3: User Boot Code area protection for a detailed description of the

UBC area.

●

DATASIZE

The DATASIZE option byte is used to configure the size of the data EEPROM area.

This option byte specifies the number of pages starting from the end of the memory.

The maximum size of the data EEPROM area is of 2 Kbytes.

Refer to STM8TL5xxx datasheet for details on DATASIZE value programming.