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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Flash Program Memory
FMKEY Register – Flash Program Memory Unlock Key Data Register
SFR Address: F9h
Bit
7
6
5
4
3
2
1
0
Name
FMKEY7
FMKEY6
FMKEY�
FMKEY4
FMKEY3
FMKEY � FMKEY 1 FMKEY 0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
Bit 7~0
Flash Memory Unlock Key Data register Unlock Data bits 7~bit 0
The FMKEY register is the Flash Memory Unlock key data register. If a correct key
data sequence has been written into this register, the Flash memory will release its
locked status; otherwise, the Flash memory will remain in its locked status. The correct
sequence to be written is 55H, AAH, 00H and then FFH. It is recommended to write
the key data sequence to the FMKEY register in four consecutive instructions. When
the program memory is in an unlocked status, writing any data to the FMKEY register
will result in the program memory being locked again. If there is no need to update the
program memory, it’s strongly recommended to lock the program memory at all times.
FMSR Register – Flash Program Memory Status Register
SFR Address: E2h
Bit
7
6
5
4
3
2
1
0
Name
UNLOCK
—
—
—
FMPF
FMSEF
FMBF
FMBUSY
R/W
R
—
—
—
R
R
R
R
POR
0
—
—
—
0
0
0
0
Bit 7
UNLOCK:
Flash memory Control Registers Unlock flag
0: Indicated Flash Memory Controller is locked
1: Indicated Flash Memory Controller is unlocked
Bit 6~4
Unimplemented, read as “0”
Bit 3
FMPF:
Flash Memory Controller Procedure flag
0: The Flash Memory Controller Procedure Flag is cleared to 0 if FMSEF=1,
or if FMBF=1 or if the IAP Procedure has ended.
1: Flash Memory Controller Procedure is corrected
Bit 2
FMSEF:
Flash Memory Controller Security Error Flag
0: Manipulation of Flash Memory does not violate the security rules
1: Manipulation of Flash Memory violates the security rules
After a flash memory manipulation, this bit must be checked to determine if the Flash
Memory manipulation has violated the security rules or not.
Bit 1
FMBF:
Flash Memory Controller Break Flag
0: Manipulation of Flash Memory does not violate the security rules or lock rules or
FMCR mode change
1: Manipulation of Flash Memory violates the security rules or lock rules or FMCR
mode change
Bit 0
FMBUSY:
Flash Memory Controller Status indication bit
0: Not erasing or rewriting
1: Busy