Am29LV800B 9
PRELIMINARY
Writing Commands/Command Sequences
To write a command or command sequence (which includes programming data to the device and erasing
sectors of memory), the system must drive WE# and
CE# to V
IL
, and OE# to VIH.
For program operations, the BYT E# pin determin es
whether the device accepts program data in bytes or
words. Refer to “Word/Byte Configuration” for more
information.
The device features an Unlock Bypass mode to facili-
tate faster programming. Once the device enters the Unlock Bypass mode, only two write cycles are required to
program a word or byte, instead of four. The “Word/Byte
Program Command Sequence” section has details on
programming data to the device using both standard and
Unlock Bypass command sequences.
An erase operation can erase one sect or, multiple sectors, or the entire device. Tables 2 and 3 indicate the
address space that each sector occupies. A “sector address” consists of the addres s bits required t o un iquely
select a sector. The “Command Definitions” section
has details on erasing a sector or the entire chip, or
suspending/resuming the erase operation.
After the system writes the autoselect command sequence, the device enters the autoselect mode. The
system can then read autoselect codes from the internal register (which is separate from the memory array)
on DQ7–DQ0. Standard read cycle timings apply in this
mode. Refer to the “Autoselect Mode” and “Autoselect
Command Sequence” sections for more information.
I
CC2
in the DC Characteristics table represents the active current specification for the w rite mode. The “AC
Characteristics” section contains timing specification
tables and timing diagrams for write operations.
Program and Erase Operation Status
During an erase or program operation, the system ma y
check the status of the operation by reading the status
bits on DQ7–DQ0. Standard read cycle timings and I
CC
read specifications apply. Refer to “Write Operation
Status” for more information, and to “AC Characteristics” for timing diagrams.
Standby Mode
When the system is not reading or writing to the device ,
it can place the device in the standby mode. In this
mode, current consumption is great ly reduc ed, and the
outputs are placed in the high impedance state, independent of the OE# input.
The device enters the CMOS standby mode when the
CE# and RESET# pin s are both held at V
CC
± 0.3 V.
(Note that this is a more restricted voltage range than
V
IH
.) If CE# and RESET# ar e held a t VIH, but not within
V
CC
± 0.3 V, the device will be in the standb y mode, b ut
the standby current will be grea ter. The device requires
standard access time (t
CE
) for read access when the
device is in either of these standby modes, before it is
ready to read data.
If the device is deselected during erasure or programming, the device draws active current until the
operation is completed.
In the DC Characteristics table, I
CC3
and I
CC4
repre-
sents the standby current specification.
Automatic Sleep Mode
The automatic sleep mode minimizes Flash device
energy consumption. The device automatically
enables this mode when addres ses remain stable for
t
ACC
+ 30 ns. The automatic sleep mode is
independent of the CE#, WE#, and OE# control
signals. Standard address access timings provide new
data when addresses are chan ged. While in sleep
mode, output data is latched and always available to
the system. I
CC4
in the DC Characteristics table
represents the automatic sleep mode current
specification.
RESET#: Hardware Reset Pin
The RESET# pin provides a hardw are method of resetting the device to reading array data. When the RESET# pin is driven low for at least a period of t
RP
, the
device immediately terminates any operation in
progress, tristates all output pins, and ignores all
read/write commands for the duration of the RESET#
pulse. The device also resets the inter nal state machine to reading array data. The operation that was interrupted should be reinitiated once the device is ready
to accept another command sequence, to ensure data
integrity.
Current is reduced for the duration of the RESET#
pulse. When RESET# is held at V
SS
±0.3 V, the device
draws CMOS standby c urrent (I
CC4
). If RESET# is held
at V
IL
but not within VSS±0.3 V, the standby current will
be greater.
The RESET# pin may be tied to the system reset cir-
cuitry. A system reset would thus also reset the Flash
memory, enabling the system to read the boot-up
firmware from the Flash memory.
If RESET# is asserted during a program or erase operation, the RY/BY# pin remains a “0” (busy) until the
internal reset operation is complete, which requires a
time of t
READY
(during Embedded Algorithms). The
system can thus monitor RY/BY# to determine
whether the reset oper ation is c omplete . If RESE T# is
asserted when a program or erase oper ation is not e xecuting (RY/BY# pin is “1”), the reset operation is
completed within a time of t
READY
(not during Embed-
ded Algorithms). The system can read data t
RH
after
the RESET# pin returns to V
IH
.