This document introduces the NuMicro M251/M252 series chip executable bit map (XOM) related configuration addresses and registers, as well as how to set or remove XOM regions
This document serves as an application note for the 32-bit NuMicro M251/M252 series, detailing the configuration of the Execute-Only Memory (XOM) region. XOM is a secure ROM region that forbids data access while allowing code execution, protecting software libraries from disassembly and copying. The note covers setting XOM size, base address, and control registers, as well as activation procedures.
| Minimum XOM size | 1 page (512 bytes) |
|---|---|
| Maximum XOM size | 512 pages (256 Kbytes) |
| XOM Region Base Address | 0x20_0000 |
| XOM Size Address | 0x20_0004 |
| XOM Control Address | 0x20_0008 |
| Default XOM Control Value (Off) | 0x5A |
| Debug Mode Control Value | 0x50 |
The minimum size for the XOM region is 1 page, which equals 512 bytes.
The M251/M252 series only allows users to set up to 1 XOM region.
Writing 0x5A to the XOM Region Control configuration indicates the XOM region is in Off mode.