512 Kbit / 1 Mbit / 2 Mbit / 4 Mbit Multi-Purpose Flash
SST39LF512 / SST39LF010 / SST39LF020 / SST39LF040
SST39VF512 / SST39VF010 / SST39VF020 / SST39VF040
Data Sheet
pulse, while the command (30H) is latched on the rising
edge of the sixth WE# pulse. The internal Erase operation
begins after the sixth WE# pulse. The End-of-Erase can be
determined using either Data# Polling or Toggle Bit meth-
ods. See Figure 9 for timing waveforms. Any commands
written during the Sector-Erase operation will be ignored.
Device Operation
Commands are used to initiate the memory operation func-
tions of the device. Commands are written to the device
using standard microprocessor write sequences. A com-
mand is written by asserting WE# low while keeping CE#
low. The address bus is latched on the falling edge of WE#
or CE#, whichever occurs last. The data bus is latched on
the rising edge of WE# or CE#, whichever occurs first.
Chip-Erase Operation
The SST39LF512/010/020/040 and SST39VF512/010/
020/040 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.
Read
The Read operation of the SST39LF512/010/020/040 and
SST39VF512/010/020/040 device is controlled by CE#
and OE#, both have to be low for the system to obtain data
from the outputs. CE# is used for device selection. When
CE# is high, the chip is deselected and only standby power
is consumed. OE# is the output control and is used to gate
data from the output pins. The data bus is in high imped-
ance state when either CE# or OE# is high. Refer to the
Read cycle timing diagram for further details (Figure 4).
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# or CE#, whichever occurs
first. During the internal Erase operation, the only valid read
is Toggle Bit or Data# Polling. See Table 4 for the command
sequence, Figure 10 for timing diagram, and Figure 18 for
the flowchart. Any commands written during the Chip-
Erase operation will be ignored.
Byte-Program Operation
The SST39LF512/010/020/040 and SST39VF512/010/
020/040 are programmed on a byte-by-byte basis. Before
programming, one must ensure that the sector, in which
the byte which is being programmed exists, is fully erased.
The Program operation consists of three steps. The first
step is the three-byte-load sequence for Software Data
Protection. The second step is to load byte address and
byte data. During the Byte-Program operation, the
addresses are latched on the falling edge of either CE# or
WE#, whichever occurs last. The data is latched on the ris-
ing edge of either CE# or WE#, whichever occurs first. The
third step is the internal Program operation which is initi-
ated after the rising edge of the fourth WE# or CE#, which-
ever occurs first. The Program operation, once initiated, will
be completed, within 20 µs. See Figures 5 and 6 for WE#
and CE# controlled Program operation timing diagrams
and Figure 15 for flowcharts. During the Program opera-
tion, the only valid reads are Data# Polling and Toggle Bit.
During the internal Program operation, the host is free to
perform additional tasks. Any commands written during the
internal Program operation will be ignored.
Write Operation Status Detection
The SST39LF512/010/020/040 and SST39VF512/010/
020/040 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 detec-
tion includes two status bits: Data# Polling (DQ7) and Tog-
gle Bit (DQ6). The End-of-Write detection mode is enabled
after the rising edge of WE# which initiates the internal Pro-
gram or Erase operation.
The actual completion of the nonvolatile write is asynchro-
nous 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 con-
flict with either DQ7 or DQ6. 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 rejec-
tion is valid.
Sector-Erase Operation
The Sector-Erase operation allows the system to erase the
device on a sector-by-sector basis. The sector architecture
is based on uniform sector size of 4 KByte. The Sector-
Erase operation is initiated by executing a six-byte-com-
mand sequence with Sector-Erase command (30H) and
sector address (SA) in the last bus cycle. The sector
address is latched on the falling edge of the sixth WE#
©2001 Silicon Storage Technology, Inc.
S71150-03-000 6/01 395
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