C8051F336_08 Datasheet, PDF (98/227 Pages) Silicon Laboratories – Mixed-Signal Byte-Programmable EPROM MCU

C8051F336/7/8/9
SFR Definition 16.2. FLKEY: Flash Lock and Key
Bit
7
6
5
4
3
2
1
0
Name
FLKEY[7:0]
Type
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xB7
Bit Name
Function
7:0 FLKEY[7:0] _{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 regis-
ter. 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 perma-
nently 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 disabled until the next reset.
98
Rev.1.0