Texas Instruments MSP430x1xx - Manual (Page 428)

Flash Memory Control Registers
C-16
C.3.3 Flash Memory Control Register FCTL3
There are no restrictions on modifying this control register. The control bits are
reset or set (WAIT) by a PUC, but key violation bit KEYV is reset by POR.
7 0
KEYV
15 8
BUSY Lock
ACCV
IFG
EMEX res. res.
FCTL3
012Ch
FCTL3 read:
FCTL3 write: 096h
0A5h
r0 r0 rw–0 rw–1 r–1 rw–0 rw–(0) r(w)–0
WAIT
BUSY 0128h, bit0, The bit BUSY shows if an access to the flash memory is possible
(BUSY=0), or if an access violation can occur. The BUSY bit is read
only, but a write operation is allowed. The BUSY bit should be tested
before each write and erase cycle. The flash-timing generator
hardware immediately sets the BUSY bit after the start of a write
operation, a segment-write operation, a segment erase, or a mass-
erase. Once the timing generator has completed its function, the BUSY
bit is reset by hardware.
The program and erase timing are shown in Figures C–7, C–8, and
C–9.
0: Flash memory is not busy. Read, write, erase and mass-erase are
possible without any violation of the internal flash timing. The
BUSY bit is reset by POR and by the flash timing generator.
1: Flash memory is busy. Remains in busy state if segment write
function is in
wait mode.
The conditions for access to the flash memory during BUSY=1 are
described in paragraph C.2.6.
KEYV, 012Ch, bit1, Key Violated.
0: Key 0A5h (high byte) was not violated.
1: Key 0A5h (high byte) was violated. Violation occurs when a write
access to register FCTL1, FCTL2 or FCTL3 is executed and the
high byte is not equal to 0A5h. If the security key is violated, bit
KEYV is set and a PUC is performed. The KEYV bit can be used
to determine the source that forced a start of the program at the
reset vector’s address. The KEYV bit is not automatically reset and
should reset by software.
Note: Any key violation results in a PUC, independent of the state of the
KEYV bit. To avoid endless software loops, the flash memory
control registers should not be written during a key violation
service routine.
Note: The software can set the KEYV bit. A PUC is also performed if
it is set by software.