Programming STM8 Flash microcontrollers

PM0051

20/27

Doc ID 14614 Rev 3

Block erase operation

The following sequence is required to perform a block erase sequence:

1.

Unlock the memory if not already done.

The UBC option byte can be read to check if the block to erase is not in the UBC area.

If necessary, reprogram it to allow erasing the targeted block.

2.

Write 0x20 in FLASH_CR2 (ERASE bit active), and 0xDF in FLASH_NCR2 (NERASE

bit active).

3.

Write '0x00 00 00 00' to any word inside the block to be erased using a LOAD

instruction.

4.

Check the WR_PG_DIS bit in FLASH_IAPSR to verify if the block you attempted to

erase was not write protected (optional).

5.

For devices with RWW capability, poll the HVOFF bit in FLASH_IAPSR register for the

start of erase operation (high voltage mode). HVOFF is reset when the erase operation

starts, thus indicating that the memory is ready for RWW.

6.

To check if the erase operation is complete, poll the EOP bit in FLASH_IAPSR from

program memory. EOP is set to ‘1’ when the block erase operation has completed. To

avoid polling the EOP bit, an interrupt can be generated when EOP is set.

Note:

It is mandatory to execute steps 2 to 5 from RAM.

Caution:

EOP and WR_PG_DIS bits are cleared by reading the FLASH_IAPSR register. It is

consequently strongly recommended to perform one single read operation to the

FLASH_IAPSR register to check the values of these bits.

Caution:

FLASH_CR2 and FLASH_NCR2 must be written consecutively to be taken into account. If

only one register is set, both are forced to their reset values, causing the erase operation to

be performed at byte level.

4.3

Word programming

Both main program memory and data EEPROM can be programmed and erased at word

level. Word operations are performed in the same way as block operations. They can be

executed either from program memory or from RAM.

When a new word program operation starts, EOP and WR_PG_DIS bits of FLASH_IAPSR

register are automatically cleared.

Contrary to word programming of the Flash program memory, the word programming of data

EEPROM with RWW feature (when available) does not stop program execution. The EOP

bit can then be used to know if the previous operation has completed. This bit is

automatically reset when reading FLASH_IAPSR.