STM8S105XX STMicroelectronics, STM8S105XX Datasheet - Page 12

• Manufacturer Part Number: STM8S105XX
• Description: (STM8S103XX / STM8S105XX) STM8S 8-bit MCU
• Manufacturer: STMicroelectronics

Product overview
12/56
Write protection (WP)
Write protection of Flash is provided to avoid unintentional overwriting of memory that could
result from a user software malfunction.
There are two levels of write protection. The first level is known as MASS (Memory Access
Security System). MASS is always enabled and protects the main Flash program memory
and option bytes.
To perform In-Application Programming (IAP), this write protection can be removed by
writing a MASS key sequence in a control register. This allows the application to modify the
contents of main program memory or the device option bytes.
A second level of write protection, can be enabled to further protect a specific area of
memory known as UBC (user boot code). Refer to
The size of the UBC is programmable through the UBC option byte
of 1 page, by programming the UBC option byte in ICP mode.
This divides the program memory into two areas:
●
●
The UBC area remains write-protected during in-application programming. This means that
the MASS keys do not unlock the UBC area. It protects the memory used to store the boot
program, specific code libraries, reset and interrupt vectors, the reset routine and usually the
IAP and communication routines.
Figure 3.
Main program memory: Up to 32 Kbytes minus UBC
User-specific boot code (UBC): Configurable up to 32 Kbytes
Up to
32 Kbytes
Flash
program
memory
Flash memory organization (STM8S105)
Remains write protected during IAP
Write access possible for IAP
Program memory area
UBC area
Figure 3.
STM8S103xx, STM8S105xx
Programmable area from 0.5 Kbytes
(2 first pages) up to 32 Kbytes
(1 page steps)
(Table
www.DataSheet4U.com
8.), in increments