C8051F70X_0910 Datasheet, PDF (141/290 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F70x/71x
21.4. EEPROM Security
RAM can only be downloaded to EEPROM after firmware writes a sequence of two bytes to EEKEY. In
order to enable EEPROM writes:
1. Write the first EEPROM key code byte to EEKEY: 0x55
2. Write the second EEPROM key code byte to EEKEY: 0xAA
After a EEPROM writes have been enabled and a single write has executed, the control logic locks
EEPROM writes until the two-byte unlock sequence has been entered into EEKEY again.
The protection state of the EEPROM can be observed by reading EEPSTATE (EEKEY2:0). This state can
be read at any time without affecting the EEPROM’s protection state.
if the two-byte unlock sequence is entered incorrectly, or if a write is attempted without first entering the
two-byte sequence, EEPROM writes will be locked until the next power-on reset.
SFR Definition 21.1. EEADDR: EEPROM Byte Address
Bit
7
6
5
4
3
2
1
0
Name
EEADDR[4:0]
Type
R
R
R
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xB6; SFR Page = All Pages
Bit
Name
Description
7:5
Unused ^{Read = 000b; Write = Don’t Care}
4:0 EEADDR[4:0] EEPROM Byte Address
Selects one of 32 EEPROM bytes to read/write.
Rev. 0.3
141