Fujitsu FR60 Hardware Manual page 568

CHAPTER 17 FLASH MEMORY
■ Sector Erase
The sector erase command sequence is executed in six access cycles. First, two "unlock" cycles are
executed, then a "Setup" command is written. After two more "unlock" cycles, the sector erase command is
entered in the sixth cycle for starting the sector erase operation. The next sector erase command can be
accepted within a time-out period of 50 µs after the last sector erase command is written.
As already mentioned, multiple sector erase commands can be accepted during the six bus cycles of the
writing operation. During the command sequence, sector erase commands (30H) for sectors whose contents
are to be erased simultaneously are written consecutively to the addresses for these sectors. The sector erase
operation itself starts from the end of the time-out period of 50 µs after the last sector erase command is
written. When the contents of multiple sectors are erased simultaneously, the subsequent sector erase
commands must be input within the 50 µs time-out period to ensure that they are accepted. For checking
whether the succeeding sector erase command is valid, read bit 3 (see "■Hardware Sequence Flag" in
Section "17.4.2 Checking the Automatic Algorithm Operating Status").
During the time-out period, any command other than sector erase and temporarily stop erase is reset at read
time, and the preceding command sequence is ignored. In the case of the temporary stop erase command,
the contends of the sector are erased again and the erase operation is completed.
Any combination and number of sector addresses can be entered in the sector erase buffers.
The user does not have to write to flash memory before the sector erase operation.
Flash memory automatically writes to all cells in a sector whose data is automatically erased (preprogram).
When the contents of a sector are erased, the other cells remain intact. In these operations, flash memory
does not have to be controlled externally.
The automatic sector erase operation starts from the end of the 50 µs time-out period after the last sector
erase command is written. When bit 7 is set to "1", the automatic sector erase operation ends and flash
memory returns to the read mode. At this time, other commands are ignored.
The data polling function is enabled for any sector address in which data has been erased. The time
required for erasing the data of multiple sectors can be expressed as follows: time for sector erase + time
for sector write (preprogram) × number of erased sectors.
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