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Flash Memory Operation
5-6
Flash Memory Controller
Initiating an Erase from Within Flash Memory
Any erase cycle can be initiated from within flash memory or from RAM. When
a flash segment erase operation is initiated from within flash memory, all timing
is controlled by the flash controller, and the CPU is held while the erase cycle
completes. After the erase cycle completes, the CPU resumes code execution
with the instruction following the dummy write.
When initiating an erase cycle from within flash memory, it is possible to erase
the code needed for execution after the erase. If this occurs, CPU execution
will be unpredictable after the erase cycle.
The flow to initiate an erase from flash is shown in Figure 5−5.
Figure 5−5. Erase Cycle from Within Flash Memory
Setup flash controller and erase
mode
Disable all interrupts and watchdog
Set LOCK=1, re-enable Interrupts
and watchdog
Dummy write
; Segment Erase from flash. 514 kHz < SMCLK < 952 kHz
; Assumes ACCVIE = NMIIE = OFIE = 0.
MOV #WDTPW+WDTHOLD,&WDTCTL ; Disable WDT
DINT ; Disable interrupts
MOV #FWKEY+FSSEL1+FN0,&FCTL2 ; SMCLK/2
MOV #FWKEY,&FCTL3 ; Clear LOCK
MOV #FWKEY+ERASE,&FCTL1 ; Enable segment erase
CLR &0FC10h ; Dummy write, erase S1
MOV #FWKEY+LOCK,&FCTL3 ; Done, set LOCK
... ; Re-enable WDT?
EINT ; Enable interrupts