Flash Memory Operation
6-11
Flash Memory Controller
6.3.3
Writing Flash Memory
The write modes, selected by the WRT and BLKWRT bits, are listed in
Table 6−3.
Table 6−4. Write Modes
BLKWRT
WRT
Write Mode
0
1
Byte/word write
1
1
Block write
Both write modes use a sequence of individual write instructions, but using the
block write mode is approximately twice as fast as byte/word mode, because
the voltage generator remains on for the complete block write. Any instruction
that modifies a destination can be used to modify a flash location in either
byte/word mode or block-write mode. A flash word (low + high byte) must not
be written more than twice between erasures. Otherwise, damage can occur.
The BUSY bit is set while a write operation is active and cleared when the
operation completes. If the write operation is initiated from RAM, the CPU must
not access flash while BUSY=1. Otherwise, an access violation occurs,
ACCVIFG is set, and the flash write is unpredictable.
Byte/Word Write
A byte/word write operation can be initiated from within flash memory or from
RAM. When initiating from within flash memory, all timing is controlled by the
flash controller, and the CPU is held while the write completes. After the write
completes, the CPU resumes code execution with the instruction following the
write. The byte/word write timing is shown in Figure 6−7.
Figure 6−7. Byte/Word Write Timing
ÎÎ
ÎÎ
Î
Î
BUSY
Programming Operation Active
Programming Time, V
CC
Current Consumption is Increased
t
Word
(see device-specific data sheet)
Generate
Programming Voltage
Remove
Programming Voltage
When a byte/word write is executed from RAM, the CPU continues to execute
code from RAM. The BUSY bit must be zero before the CPU accesses flash
again, otherwise an access violation occurs, ACCVIFG is set, and the write
result is unpredictable.
Summary of Contents for MSP430x4xx Family
Page 1: ...MSP430x4xx Family 2007 Mixed Signal Products User s Guide SLAU056G ...
Page 2: ......
Page 6: ...vi ...
Page 114: ...3 76 RISC 16 Bit CPU ...
Page 304: ...5 20 FLL Clock Module ...
Page 340: ...7 8 Supply Voltage Supervisor ...
Page 348: ...8 8 16 Bit Hardware Multiplier ...
Page 372: ...9 24 32 Bit Hardware Multiplier ...
Page 400: ...10 28 DMA Controller ...
Page 428: ...13 10 Basic Timer1 ...
Page 466: ...15 24 Timer_A ...
Page 522: ...17 30 USART Peripheral Interface UART Mode ...
Page 544: ...18 22 USART Peripheral Interface SPI Mode ...
Page 672: ...23 12 Comparator_A ...
Page 692: ...24 20 LCD Controller ...
Page 746: ...26 28 ADC12 ...