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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Flash Program Memory
Byte Write Operation
The Flash Memory must be first unlocked before implementing a Byte Write procedure. The first
step is to assign the target memory page and erase it. Refer to the Page Erase Operation section
for details. The Flash Memory Byte Write function is controlled by the control bits, FMCR.0 and
FMCR.6, in the FMCR register. Data is first written into the FMDR register to update the Page
Buffer. The Flash memory will check if the memory address has reached the page boundary. If the
boundary has been reached or there is no more data, then set the FMCR.0 bit to high to enable the
Byte Write function. When the FMCR.7 bit is set high the Byte Write procedure will be executed.
When the procedure is ready, the MCU will continue to run automatically. The following flowchart
illustrates the Byte Write procedure.
START
MCU waits fo� memo��
d�mp finished and then
MCU contin�es to ��n.
Flash memo�� cont�olle�
m�st be In �nlocked state
W�ite FMAR�
W�ite FMAR1
W�ite FMAR0
FMCR Bit 0 = 1 and
FMCR Bit 6 = 0 (*)
Ente� memo��
d�mp p�oced��e
W�ite next page
if desi�ed
MCU waits fo� b�te-w�iting
finished and then
MCU contin�es to ��n.
FMCR Bit 7 = 1
Update the Page B�ffe�
B� w�iting FMDR
FMARx �each the
page bo�nda��?
Mo�e Data?
No
Yes
No
Yes
Check FMSR Bit 1 = 1
Yes
No
Byte Write Flowchart (FMCR.0=1, FMCR.6=0)