1 Megabit Page-Mode EEPROM
SST29EE010 / SST29LE010 / SST29VE010
Write Operation Status Detection
The SST29EE010/29LE010/29VE010 provide two soft-
ware means to detect the completion of a Write 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 WE# or CE# whichever
occurs first, which initiates the internal write cycle.
The actual completion of the nonvolatile write is asyn-
chronous 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 conflict 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 rejection is valid.
Data# Polling (DQ
7
)
When the SST29EE010/29LE010/29VE010 are in the
internal write cycle, any attempt to read DQ
7
of the last
byte loaded during the byte-load cycle will receive the
complement of the true data. Once the Write cycle is
completed, DQ
7
will show true data. The device is then
ready for the next operation. See Figure 6 for Data#
Polling timing diagram and Figure 15 for a flowchart.
Toggle Bit (DQ
6
)
During the internal write cycle, any consecutive attempts
to read DQ
6
will produce alternating 0’s and 1’s, i.e.
toggling between 0 and 1. When the Write cycle is
completed, the toggling will stop. The device is then
ready for the next operation. See Figure 7 for Toggle Bit
timing diagram and Figure 15 for a flowchart. The initial
read of the Toggle Bit will typically be a “1”.
Data Protection
The SST29EE010/29LE010/29VE010 provide both
hardware and software features to protect nonvolatile
data from inadvertent writes.
Hardware Data Protection
Noise/Glitch Protection: A WE# or CE# pulse of less than
5 ns will not initiate a Write cycle.
V
CC
Power Up/Down Detection: The Write operation is
inhibited when V
CC
is less than 2.5V.
Write Inhibit Mode: Forcing OE# low, CE# high, or WE#
high will inhibit the Write operation. This prevents inad-
vertent writes during power-up or power-down.
Software Data Protection (SDP)
The SST29EE010/29LE010/29VE010 provide the
JEDEC approved optional Software Data Protection
scheme for all data alteration operations, i.e., Write and
Chip-Erase. With this scheme, any Write operation re-
quires the inclusion of a series of three byte-load opera-
tions to precede the data loading operation. The three
byte-load sequence is used to initiate the Write cycle,
providing optimal protection from inadvertent write opera-
tions, e.g., during the system power-up or power-down.
The SST29EE010/29LE010/29VE010 are shipped with
the Software Data Protection disabled.
The software protection scheme can be enabled by
applying a three-byte sequence to the device, during a
page-load cycle (Figures 4 and 5). The device will then
be automatically set into the data protect mode. Any
subsequent Write operation will require the preceding
three-byte sequence. See Table 4 for the specific soft-
ware command codes and Figures 4 and 5 for the timing
diagrams. To set the device into the unprotected mode,
a six-byte sequence is required. See Table 4 for the
specific codes and Figure 8 for the timing diagram. If a
write is attempted while SDP is enabled the device will be
in a non-accessible state for ~ 300 µs. SST recommends
Software Data Protection always be enabled. See Figure
16 for flowcharts.
The SST29EE010/29LE010/29VE010 Software Data
Protection is a global command, protecting
(or unprotecting) all pages in the entire memory array
once enabled (or disabled). Therefore using SDP for a
single Page-Write will enable SDP for the entire array.
Single pages by themselves cannot be SDP enabled or
disabled.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
© 2000 Silicon Storage Technology, Inc.
3
304-3 6/00
SST [ SILICON STORAGE TECHNOLOGY, INC ]
