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CHAPTER 21 FLASH MEMORY
21.6.3 Erasing data
There are two methods for erasing data in this device. One is chip erase and the other
is sector erase. Chip erase is used to erase the data of the whole chip and sector erase
is used to erase data in units of sectors.
■
Chip erase
All data can be erased from the flash memory by continuously transmitting the Chip Erase
command from the command sequence table to target sectors in the flash memory.
Chip erase requires six bus cycles. The chip erase operation starts after writing in the 6th cycle
is completed. With chip erase, the user need not write data to the flash memory prior to erase.
During execution of the automatic erase algorithm, the flash memory automatically writes 0 for
verification before erasing all cells.
■
Sector erase
Sector erase can erase data in units of sectors. The user can specify several sectors at the
same time.
Target sectors in flash memory can be erased by continuously transmitting the Sector Erase
command from the command sequence table (Table 21.4-1 "Command sequence") to those
sectors.
❍
Sector specification method
Sector erase requires six bus cycles. 50
µ
s sector erase wait is started by writing the sector
erase code (30H) at any even address that can be accessed in a target sector in the 6th cycle.
Multiple sector erase is enabled by writing the sector erase code (30H) at an address in the
target sector to be erased after the above processing is finished.
❍
Note on specifying multiple sectors
Erase is started after the period from writing of the last sector erase code to when the 50
µ
s
sector erase wait time elapsed. That is, to erase multiple sectors at the same time, it is
necessary to enter the next erase sector address and an erase code (in the 6th cycle of the
command sequence) within 50
µ
s. Erase sector addresses and erase codes entered after the
50
µ
s have elapsed may not be accepted. The sector erase timer (hardware sequence flag
SETIMR) can be used to check whether writing of the subsequent sector erase codes was
effective. In this case, however, the address from which the sector erase timer is read must
indicate the sector to be erased.
❍
Sector erase procedure
Using hardware sequence flags enables to determine the status of the automatic algorithm in
the flash memory. Figure 21.6-2 "Example of the procedure for flash memory sector erase" is an
example of the flash memory sector erase procedure. Here, the toggle bit flag (TOGGLE) is
used to check for the end of erase processing.
Note that data for flag check is read from the sector to be erased.
When the timing limit excess flag (TLOVER) changes to 1, the toggle bit flag (TOGGLE) stops
the toggle operation at the same time. For this reason, even if (TLOVER) is 1, (TOGGLE) must
be rechecked.
Содержание MB91150 Series
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Страница 3: ...FUJITSU LIMITED FR30 32 BIT MICROCONTROLLER MB91150 Series HARDWARE MANUAL ...
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Страница 112: ...96 CHAPTER 3 MEMORY SPACE CPU AND CONTROL UNIT ...
Страница 174: ...158 CHAPTER 5 I O PORTS Note DDRI bit 6 is a test bit Always set the bit to 0 The value read from this bit is always 0 ...
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Страница 214: ...198 CHAPTER 7 16 BIT RELOAD TIMER ...
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Страница 420: ...404 CHAPTER 19 PERIPHERAL STOP CONTROL ...
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Страница 503: ...487 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
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