AM29F400B AMD [Advanced Micro Devices], AM29F400B Datasheet - Page 8

• Manufacturer Part Number: AM29F400B
• Description: 4 Megabit (512 K x 8-Bit/256 K x 16-Bit) CMOS 5.0 Volt-only Boot Sector Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

After the system writes the autoselect command se-
quence, the device enters the autoselect mode. The
system can then read autoselect codes from the inter-
nal 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
tive current specification for the write 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 may
check the status of the operation by reading the status
bits on DQ7–DQ0. Standard read cycle timings and I
read specifications apply. Refer to “Write Operation
Status” for more information, and to “AC Characteris-
tics” 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 greatly reduced, and the
outputs are placed in the high impedance state, inde-
pendent of the OE# input.
The device enters the CMOS standby mode when the
CE# and RESET# pins are both held at V
(Note that this is a more restricted voltage range than
V
CE# and RESET# pins are both held at V
requires standard access time (t
when the device is in either of these standby modes,
before it is ready to read data.
The device also enters the standby mode when the RE-
SET# pin is driven low. Refer to the next section, “RE-
SET#: Hardware Reset Pin”.
If the device is deselected during erasure or program-
ming, the device draws active current until the
operation is completed.
8
CC2
IH
.) The device enters the TTL standby mode when
in the DC Characteristics table represents the ac-
CE
) for read access
IH
. The device
CC
P R E L I M I N A R Y
0.5 V.
Am29F400B
CC
In the CMOS and TTL/NMOS-compatible DC Charac-
teristics tables, I
specification.
RESET#: Hardware Reset Pin
The RESET# pin provides a hardware method of reset-
ting the device to reading array data. When the RE-
SET# pin is driven low for at least a period of t
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 internal state ma-
chine to reading array data. The operation that was in-
terrupted 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
the TTL standby mode; if RESET# is held at V
V, the device enters the CMOS standby mode.
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 oper-
ation, the RY/BY# pin remains a “0” (busy) until the in-
ternal reset operation is complete, which requires a
time of t
system can thus monitor RY/BY# to determine whether
the reset operation is complete. If RESET# is asserted
when a program or erase operation is not executing
(RY/BY# pin is “1”), the reset operation is completed
within a time of t
rithms). The system can read data t
SET# pin returns to V
Refer to the AC Characteristics tables for RESET# pa-
rameters and to Figure 10 for the timing diagram.
Output Disable Mode
When the OE# input is at V
disabled. The output pins are placed in the high imped-
ance state.
READY
(during Embedded Algorithms). The
CC3
READY
IH
represents the standby current
.
(not during Embedded Algo-
IH
, output from the device is
IL
, the device enters
RH
after the RE-
SS
RP,
±0.5
the