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.
The Read operation of the SST39WF800A 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
impedance state when either CE# or OE# is high. Refer to
the Read cycle timing diagram for further details (Figure 4).
The SST39WF800A is programmed on a word-by-word
basis. Before programming, the sector where the word
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 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 initiated after the rising edge of
the fourth WE# or CE#, whichever occurs first. The Pro-
gram operation, once initiated, will be completed within 40
µs. See Figures 5 and 6 for WE# and CE# controlled Pro-
gram operation timing diagrams and Figure 15 for flow-
charts. During the Program operation, the only valid reads
are Data# Polling and Toggle Bit. During the internal Pro-
gram operation, the host is free to perform additional tasks.
Any commands issued during the internal Program opera-
tion are ignored.
8 Mbit Multi-Purpose Flash
The Sector- (or Block-) Erase operation allows the system
to erase the device on a sector-by-sector (or block-by-
block) basis. The SST39WF800A 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-
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.
The SST39WF800A provides 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
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 18 for the flowchart. Any commands issued dur-
ing the Chip-Erase operation are ignored.
©2006 Silicon Storage Technology, Inc.