SST49LF080A Datasheet, PDF (18/50 Pages) Silicon Storage Technology, Inc – 8 Mbit LPC Flash

8 Mbit LPC Flash
SST49LF080A
Chip-Erase Operation
Data Sheet
The SST49LF080A devices provide a Chip-Erase operation, which allows the user to erase the entire
memory array to the “1s” state. This is useful when the entire device must be quickly erased.
The Chip-Erase operation is initiated by executing a six- byte Software Data Protection command
sequence with Chip-Erase command (10H) with address 5555H in the last byte sequence. The internal
Erase operation begins with the rising edge of the sixth WE#. During the internal Erase operation, the
only valid read is Toggle Bit or Data# Polling. See Table 11 for the command sequence, Figure 25 for
Chip-Erase timing diagram, and Figure 37 for the flowchart. Any commands written during the Chip-
Erase operation will be ignored.
Write Operation Status Detection
The SST49LF080A devices provide two software means to detect the completion of a Write (Program
or Erase) cycle, in order to optimize the system Write cycle time. The software detection includes two
status bits: Data# Polling D[7] and Toggle Bit D[6]. The End-of-Write detection mode is enabled after
the rising edge of WE# which initiates the internal Program or Erase operation.
The actual completion of the nonvolatile write is asynchronous with the system; therefore, either a
Data# Polling or Toggle Bit read may be simultaneous with the completion of the Write cycle. If this
occurs, the system may possibly get an erroneous result, i.e., valid data may appear to conflict with
either D[7] or D[6]. In order to prevent spurious rejection, if an erroneous result occurs, the software
routine should include a loop to read the accessed location an additional two (2) times. If both reads
are valid, then the device has completed the Write cycle, otherwise the rejection is valid.
Data# Polling (DQ₇)
When the SST49LF080A device is in the internal Program operation, any attempt to read DQ₇ will pro-
duce the complement of the true data. Once the Program operation is completed, DQ₇ will produce
true data. Note that even though DQ₇ may have valid data immediately following the completion of an
internal Write operation, the remaining data outputs may still be invalid: valid data on the entire data
bus will appear in subsequent successive Read cycles after an interval of 1 µs. During internal Erase
operation, any attempt to read DQ₇ will produce a ‘0’. Once the internal Erase operation is completed,
DQ₇ will produce a ‘1’. The Data# Polling is valid after the rising edge of fourth WE# pulse for Program
operation. For Sector-, Block-, or Chip-Erase, the Data# Polling is valid after the rising edge of sixth
WE# pulse. See Figure 20 for Data# Polling timing diagram and Figure 35 for a flowchart. Proper sta-
tus will not be given using Data# Polling if the address is in the invalid range.
©2014 Silicon Storage Technology, Inc.
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