Samsung C8278X ユーザーズマニュアル

The FMUSR register is used for a safety operation of the flash memory. This register will protect undesired erase 
or program operation from malfunctioning of CPU caused by an electrical noise. After reset, the user-programming 
mode is disabled, because the value of FMUSR is "00000000B" by reset operation. If necessary to operate the 
flash memory, you can use the user programming mode by setting the value of FMUSR to "10100101B". The 
other value of "10100101b", user program mode is disabled.   

Flash Memory User Programming Enable Register (FMUSR)

F1H, Set 1, Bank 1, R/W

.7

.6

.5

.4

.3

.2

.1

.0

MSB

LSB

Flash memory user programming enable bits:
10100101: Enable user programming mode
Other values: Disable user programming mode