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Flash Memory Operation
5-7
Flash Memory Controller
Initiating an Erase from RAM
Any erase cycle may be initiated from RAM. In this case, the CPU is not held
and can continue to execute code from RAM. The BUSY bit must be polled to
determine the end of the erase cycle before the CPU can access any flash
address again. If a flash access occurs while BUSY=1, it is an access violation,
ACCVIFG will be set, and the erase results will be unpredictable.
The flow to initiate an erase from flash from RAM is shown in Figure 5−6.
Figure 5−6. Erase Cycle from Within RAM
yes
BUSY = 1
yes
BUSY = 1
Disable all interrupts and watchdog
Setup flash controller and
erase mode
Dummy write
Set LOCK = 1, re-enable
interrupts and watchdog
; Segment Erase from RAM. 514 kHz < SMCLK < 952 kHz
; Assumes ACCVIE = NMIIE = OFIE = 0.
MOV #WDTPW+WDTHOLD,&WDTCTL ; Disable WDT
DINT ; Disable interrupts
L1 BIT #BUSY,&FCTL3 ; Test BUSY
JNZ L1 ; Loop while busy
MOV #FWKEY+FSSEL1+FN0,&FCTL2 ; SMCLK/2
MOV #FWKEY,&FCTL3 ; Clear LOCK
MOV #FWKEY+ERASE,&FCTL1 ; Enable erase
CLR &0FC10h ; Dummy write, erase S1
L2 BIT #BUSY,&FCTL3 ; Test BUSY
JNZ L2 ; Loop while busy
MOV #FWKEY+LOCK,&FCTL3 ; Done, set LOCK
... ; Re-enable WDT?
EINT ; Enable interrupts