Texas Instruments MSP430x1xx User 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.

KEYV

BUSY

Lock

ACCV

IFG

EMEX

res.

FCTL3

012Ch

FCTL3 read:
FCTL3 write:

096h

0A5h

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.

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.

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.

Key 0A5h (high byte) was not violated.

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.