©2012 Silicon Storage Technology, Inc. DS25023B 06/13
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1 Mbit / 2 Mbit / 4 Mbit Multi-Purpose Flash
SST39LF010 / SST39LF020 / SST39LF040
SST39VF010 / SST39VF020 / SST39VF040
Data Sheet
Device Operation
Commands are used to initiate the memory operation functions of the device. Commands are written
to the device using standard microprocessor write sequences. A command 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 SST39LF010/020/040 and SST39VF010/020/040 devices are 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 impedance
state when either CE# or OE# is high. Refer to the Read cycle timing diagram for further details (Figure
4).
Byte-Program Operation
The SST39LF010/020/040 and SST39VF010/020/040 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 Protec-
tion. 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
Program 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 Pro-
gram operation will be ignored.
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 command 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# 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 methods. See Figure 9 for timing waveforms. Any commands written during the
Sector-Erase operation will be ignored.
Chip-Erase Operation
The SST39LF010/020/040 and SST39VF010/020/040 devices provide a Chip-Erase operation, which
allows the user to erase the entire memory array to the ‘1’s 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# or CE#, whichever occurs first. During the
