cured Silicon Sector region by issuing the three-cycle
Enter Secured Silicon Sector command sequence.
The device continues to access the Secured Silicon
Sector region until the system issues the four-cycle
Exit Secured Silicon Sector command sequence. The
Exit Secured Silicon Sector command sequence re-
turns the device to normal operation. The Secured Sil-
icon Sector is not accessible when the device is
executing an Embedded Program or embedded Erase
algorithm. Table 12 shows the address and data re-
quirements for both command sequences. See also
“Secured Silicon Sector Flash Memory Region” for fur-
ther information. Note that the ACC function and un-
lock bypass modes are not available when the
Secured Silicon Sector is enabled.
from “0” back to a “1.” Attempting to do so may
cause that bank to set DQ5 = 1, or cause the DQ7 and
DQ6 status bits to indicate the operation was success-
ful. However, a succeeding read will show that the
data is still “0.” Only erase operations can convert a “0”
to a “1.”
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram bytes or words to a bank faster than using the
standard program command sequence. The unlock
bypass command sequence is initiated by first writing
two unlock cycles. This is followed by a third write
cycle containing the unlock bypass command, 20h.
That bank then enters the unlock bypass mode. A
two-cycle unlock bypass program command sequence
is all that is required to program in this mode. The first
cycle in this sequence contains the unlock bypass pro-
gram command, A0h; the second cycle contains the
program address and data. Additional data is pro-
grammed in the same manner. This mode dispenses
with the initial two unlock cycles required in the stan-
dard program command sequence, resulting in faster
total programming time. Table 12 shows the require-
ments for the command sequence.
Byte/Word Program Command Sequence
The system may program the device by word or byte,
depending on the state of the BYTE# pin. Program-
ming is a four-bus-cycle operation. The program com-
mand sequence is initiated by writing two unlock write
cycles, followed by the program set-up command. The
program address and data are written next, which in
turn initiate the Embedded Program algorithm. The
system is not required to provide further controls or
timings. The device automatically provides internally
generated program pulses and verifies the pro-
grammed cell margin. Table 12 shows the address and
data requirements for the byte program command se-
quence.
During the unlock bypass mode, only the Unlock By-
pass Program and Unlock Bypass Reset commands
are valid. To exit the unlock bypass mode, the system
must issue the two-cycle unlock bypass reset com-
mand sequence. (See Table 12).
When the Embedded Program algorithm is complete,
that bank then returns to the read mode and ad-
dresses are no longer latched. The system can deter-
mine the status of the program operation by using
DQ7, DQ6, or RY/BY#. Refer to the Write Operation
Status section for information on these status bits.
The device offers accelerated program operations
through the WP#/ACC pin. When the system asserts
VHH on the WP#/ACC pin, the device automatically en-
ters the Unlock Bypass mode. The system may then
write the two-cycle Unlock Bypass program command
sequence. The device uses the higher voltage on the
WP#/ACC pin to accelerate the operation. Note that
the WP#/ACC pin must not be at VHH for any operation
other than accelerated programming, or device dam-
age may result. In addition, the WP#/ACC pin must not
be left floating or unconnected; inconsistent behavior
of the device may result.
Any commands written to the device during the Em-
bedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program
operation. The program command sequence should
be reinitiated once that bank has returned to the read
mode, to ensure data integrity. Note that the Secured
Silicon Sector, autoselect, and CFI functions are un-
available when a program operation is in progress.
Figure 4 illustrates the algorithm for the program oper-
ation. Refer to the Erase and Program Operations
table in the AC Characteristics section for parameters,
and Figure 18 for timing diagrams.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
24
Am29DL640H
June 7, 2005
SPANSION [ SPANSION ]
