2 Mbit / 4 Mbit / 8 Mbit Multi-Purpose Flash
SST39LF200A / SST39LF400A / SST39LF800A
SST39VF200A / SST39VF400A / SST39VF800A
Data Sheet
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.
Read
The Read operation of the SST39LF200A/400A/800A and
SST39VF200A/400A/800A 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 con-
sumed. 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 for further details (Figure 3).
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 Block-Erase
operation is initiated by executing a six-byte command
sequence with Block-Erase command (50H) and block
address (BA) in the last bus cycle. The sector or block
address is latched on the falling edge of the sixth WE#
pulse, while the command (30H or 50H) 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 operation can be determined using either Data#
Polling or Toggle Bit methods. See Figures 9 and 10 for tim-
ing waveforms. Any commands issued during the Sector-
or Block-Erase operation are ignored.
Chip-Erase Operation
The SST39LF200A/400A/800A and SST39VF200A/400A/
800A provide a Chip-Erase operation, which allows the
user to erase the entire memory array to the “1” state. This
is useful when the entire device must be quickly erased.
The Chip-Erase operation is initiated by executing a six-
byte command sequence with Chip-Erase command (10H)
at address 5555H in the last byte sequence. The Erase
operation begins with the rising edge of the sixth WE# or
CE#, whichever occurs first. During the Erase operation,
the only valid read is Toggle Bit or Data# Polling. See Table
4 for the command sequence, Figure 8 for timing diagram,
and Figure 19 for the flowchart. Any commands issued dur-
ing the Chip-Erase operation are ignored.
Word-Program Operation
The SST39LF200A/400A/800A and SST39VF200A/400A/
800A are programmed on a word-by-word basis. Before
programming, one must ensure that the sector, in which
the word 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 Pro-
tection. The second step is to load word address and word
data. During the Word-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 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 4 and 5 for WE#
and CE# controlled Program operation timing diagrams
and Figure 16 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 issued during the
internal Program operation are ignored.
Write Operation Status Detection
The SST39LF200A/400A/800A and SST39VF200A/400A/
800A 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 (DQ
7
) and Toggle Bit (DQ
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 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 DQ
7
or DQ
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 rejec-
tion is valid.
Sector/Block-Erase Operation
The Sector- (or Block-) Erase operation allows the system
to erase the device on a sector-by-sector (or block-by-
block) basis. The SST39LF200A/400A/800A and
SST39VF200A/400A/800A offers both Sector-Erase and
Block-Erase mode. The sector architecture is based on
uniform sector size of 2 KWord. The Block-Erase mode is
based on uniform block size of 32 KWord. The Sector-
©2001 Silicon Storage Technology, Inc.
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