C8051F85X86X Datasheet, PDF (60/290 Pages) Silicon Laboratories – Low-Cost 8-bit MCU Family with up to 8 kB of Flash

C8051F85x/86x
Register 10.2. FLKEY: Flash Lock and Key
Bit
7
Name
Type
Reset
0
SFR Address: 0xB7
Bit
Name
7:0
FLKEY
6
5
4
3
2
1
0
FLKEY
RW
0
0
0
0
0
0
0
Table 10.3. FLKEY Register Bit Descriptions
Function
Flash Lock and Key Register.
Write:
This register provides a lock and key function for flash erasures and writes. Flash writes
and erases are enabled by writing 0xA5 followed by 0xF1 to the FLKEY register. Flash
writes and erases are automatically disabled after the next write or erase is complete. If
any writes to FLKEY are performed incorrectly, or if a flash write or erase operation is
attempted while these operations are disabled, the flash will be permanently locked from
writes or erasures until the next device reset. If an application never writes to flash, it can
intentionally lock the flash by writing a non-0xA5 value to FLKEY from software.
Read:
When read, bits 1-0 indicate the current flash lock state.
00: Flash is write/erase locked.
01: The first key code has been written (0xA5).
10: Flash is unlocked (writes/erases allowed).
11: Flash writes/erases are disabled until the next reset.
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