AM29SL400DB90 SPANSION [SPANSION], AM29SL400DB90 Datasheet - Page 16

• Manufacturer Part Number: AM29SL400DB90
• Description: 4 Megabit (512 K x 8-Bit/256 K x 16-Bit) CMOS 1.8 Volt-only Super Low Voltage Flash Memory
• Manufacturer: SPANSION [SPANSION]

before erasing begins. This resets the device to reading
array data. Once erasure begins, however, the device
ignores reset commands until the operation is com-
plete.
The reset command may be written between the
sequence cycles in a program command sequence
before programming begins. This resets the device to
reading array data (also applies to programming in
Erase Suspend mode). Once programming begins,
however, the device ignores reset commands until the
operation is complete.
The reset command may be written between the
sequence cycles in an autoselect command sequence.
Once in the autoselect mode, the reset command must
be written to return to reading array data (also applies
to autoselect during Erase Suspend).
If DQ5 goes high during a program or erase operation,
writing the reset command returns the device to
reading array data (also applies during Erase Sus-
pend).
Autoselect Command Sequence
The autoselect command sequence allows the host
system to access the manufacturer and devices codes,
and determine whether or not a sector is protected.
Table 5 on page 17
requirements. This method is an alternative to that
shown in
PROM programmers and requires V
A9.
The autoselect command sequence is initiated by
writing two unlock cycles, followed by the autoselect
command. The device then enters the autoselect
mode, and the system may read at any address any
number of times, without initiating another command
sequence. A read cycle at address XX00h retrieves the
manufacturer code. A read cycle at address 01h in
word mode (or 02h in byte mode) returns the device
code. A read cycle containing a sector address (SA)
and the address 02h in word mode (or 04h in byte
mode) returns 01h if that sector is protected, or 00h if it
is unprotected. Refer to
on page 10
The system must write the reset command to exit the
autoselect mode and return to reading array data.
Word/Byte 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
command 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 tim-
14
Table 4 on page
for valid sector addresses.
shows the address and data
Table 2 on page 10
11, which is intended for
A D V A N C E
ID
on address bit
and
Table 3
Am29SL400D
I N F O R M A T I O N
ings. The device automatically generates the program
pulses and verifies the programmed cell margin.
Table 5 on page 17
r e q u i re m en t s fo r th e byt e pr o gra m c om m a n d
sequence.
When the Embedded Program algorithm is complete,
the device then returns to reading array data and
addresses are no longer latched. The system can
determine the status of the program operation by using
D Q 7, D Q 6, or RY/B Y# . Se e W r i te Op e ra tio n
Status, on page 18 for information on these status bits.
Any commands written to the device during the
Embedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program-
m i n g o pe rat io n. T h e B yte Pr o gra m com m a n d
sequence should be reinitiated once the device has
reset to reading array data, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from a “0” back to a “1”. Attempting to do so may halt
the operation and set DQ5 to “1”, or cause the Data#
Polling algorithm 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”.
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to
program bytes or words to the device 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. The
device 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
program 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. Write Operation Status, on
page 18 shows the requirements for the command
sequence.
During the unlock bypass mode, only the Unlock
Bypass Program and Unlock Bypass Reset commands
are valid. To exit the unlock bypass mode, the system
mus t issue the two-cyc le unlock bypas s reset
command sequence. The first cycle must contain the
data 90h; the second cycle the data 00h. Addresses
are don’t cares. The device then returns to reading
array data.
Figure 3, on page 15
p r o g r a m o p e r a t i o n . S e e t h e E r a s e / P r o g r a m
shows the address and data
illustrates the algorithm for the
Rev. A Amend. +1 April 13, 2005