D A T A S H E E T
When the Embedded Program algorithm is complete,
by a third write cycle containing the Write Buffer Load
command written at the Sector Address in which pro-
gramming will occur. The fourth cycle writes the sector
address and the number of word locations, minus one,
to be programmed. For example, if the system will pro-
gram 6 unique address locations, then 05h should be
written to the device. This tells the device how many
write buffer addresses will be loaded with data and
therefore when to expect the Program Buffer to Flash
command. The number of locations to program cannot
exceed the size of the write buffer or the operation will
abort.
the device 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 or DQ6. Refer to the Write Operation Status sec-
tion for information on these status bits.
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 the device has returned to the read
mode, to ensure data integrity. Note that the ACC
function and unlock bypass modes are not available
when the SecSi Sector is enabled.
The fifth cycle writes the first address location and
data to be programmed. The write-buffer-page is se-
lected by address bits AMAX–A4. All subsequent ad-
dress/data pairs must fall within the
selected-write-buffer-page. The system then writes the
remaining address/data pairs into the write buffer.
Write buffer locations may be loaded in any order.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from “0” back to a “1.” Attempting to do so may
cause the device to set DQ5 = 1, or cause the DQ7
and DQ6 status bits to indicate the operation was suc-
cessful. However, a succeeding read will show that the
data is still “0.” Only erase operations can convert a “0”
to a “1.”
The write-buffer-page address must be the same for
all address/data pairs loaded into the write buffer.
(This means Write Buffer Programming cannot be per-
formed across multiple write-buffer pages. This also
means that Write Buffer Programming cannot be per-
formed across multiple sectors. If the system attempts
to load programming data outside of the selected
write-buffer page, the operation will abort.
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram words to the device faster than using the stan-
dard program command sequence. The unlock bypass
command sequence is initiated by first writing two un-
lock cycles. This is followed by a third write cycle con-
taining the unlock bypass command, 20h. The device
then enters the unlock bypass mode. A two-cycle un-
lock bypass program command sequence is all that is
required to program in this mode. The first cycle in this
sequence contains the unlock bypass program com-
mand, A0h; the second cycle contains the program
address and data. Additional data is programmed in
the same manner. This mode dispenses with the initial
two unlock cycles required in the standard program
command sequence, resulting in faster total program-
ming time. Tables 10 and 11 show the requirements
for the command sequence.
Note that if a Write Buffer address location is loaded
multiple times, the address/data pair counter will be
decremented for every data load operation. The host
system must therefore account for loading a
write-buffer location more than once. The counter
decrements for each data load operation, not for each
unique write-buffer-address location. Note also that if
an address location is loaded more than once into the
buffer, the final data loaded for that address will be
programmed.
Once the specified number of write buffer locations
have been loaded, the system must then write the Pro-
gram Buffer to Flash command at the sector address.
Any other address and data combination aborts the
Write Buffer Programming operation. The device then
begins programming. Data polling should be used
while monitoring the last address location loaded into
the write buffer. DQ7, DQ6, DQ5, and DQ1 should be
monitored to determine the device status during Write
Buffer Programming.
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. The first cycle must contain the data
90h. The second cycle must contain the data 00h. The
device then returns to the read mode.
The write-buffer programming operation can be sus-
pended using the standard program suspend/resume
commands. Upon successful completion of the Write
Buffer Programming operation, the device is ready to
execute the next command.
Write Buffer Programming
Write Buffer Programming allows the system write to a
maximum of 16 words/32 bytes in one programming
operation. This results in faster effective programming
time than the standard programming algorithms. The
Write Buffer Programming command sequence is initi-
ated by first writing two unlock cycles. This is followed
The Write Buffer Programming Sequence can be
aborted in the following ways:
26
Am29LV640MH/L
December 14, 2005
SPANSION [ SPANSION ]
