1 Mbit / 2 Mbit / 4 Mbit Multi-Purpose Flash
SST39SF010A / SST39SF020A / SST39SF040
Data Sheet
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 methods. 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 SST39SF010A/020A/040 provide Chip-Erase opera-
tion, 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 SST39SF010A/020A/040 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 dese-
lected 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 impedance state when
either CE# or OE# is high. Refer to the Read cycle timing
diagram (Figure 4) for further details.
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 SST39SF010A/020A/040 are programmed on a byte-
by-byte basis. Before programming, the sector where the
byte exists must be fully erased. The Program operation is
accomplished in 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 rising edge of either CE# or WE#,
whichever occurs first. The third step is the internal Pro-
gram operation which is initiated after the rising edge of the
fourth WE# or CE#, whichever 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 operation, 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 SST39SF010A/020A/040 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
(DQ7) and Toggle Bit (DQ6). The End-of-Write detection
mode is enabled after the rising edge of WE# which ini-
tiates the internal Program 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 load sequence for Software Data Protection with
Sector-Erase command (30H) and sector address (SA) in
the last bus cycle. The sector address is latched on the fall-
ing edge of the sixth WE# pulse, while the command (30H)
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