STM8S-----option byte

Option Byte ( O p t i o n B y t e )

The configuration word of the STM8S is similar to the Fuse bit of the AVR.It is used to configure the port's multiplexing function and read protection and other operations.Different from the fuse bit of AVR, the clock configuration of STM8S is not in Option Byte, and there will be no embarrassment that the chip is directly locked after writing STM8S.Option bytes are used to configure hardware features and memory protection status and are located in a specific memory array on the same page
.The option byte can be modified in ICP / SW IM mode or in I AP mode, that is, the configuration word can be written through STlink, or the option word can be written through the program
When the second function of the port needs to be enabled, it needs to be consideredOption byte programming, otherwise it will not be able to achieve the desired function of the program

For example: S TM8S has a buzzer controller B E E P, the corresponding port of this B E E P is PD 4. But PD 4 has two multiplexing functions, it can be

1.AFR7 = 1, BEEP buzzer output
2.AFR7 = 0, Tim2 compare output 1 is Tim2_CC1

Users must choose one of these two functions, only one.So how do you make PD 4 a B E E P output?The answer is to configure AF R 7 as 1 by setting the Opt ion by t e
option word, and use PD 4 to output the signal of BEE P, otherwise, PD 4 will output the signal of Tim 2 _ C C 1.
Of course, with any configuration, users can still use PD 4 like normal IO.

Optio n Byte In addition to being able to configure the multiplexing function of the port, it can also set the chip's read protection when the ROP byte in the option byte is programmed as '0 x AA'.In this case, regardless of whether the write protection is in effect, reading or modifying the FLASH program memory and DATA area in ICP mode (using the SWIM interface) is prohibited.Even if no protection is considered completely unbreakable, the STM8's read-protect feature provides a very high level of protection for a general-purpose microprocessor.That is to say, the way to prevent others from copying your program can be to program the ROP byte to enable read protection, then the other party cannot read your Flash data from STM8 no matter what