PRELIMINARY
Am29F400B
4 Megabit (512 K x 8-Bit/256 K x 16-Bit)
CMOS 5.0 Volt-only Boot Sector Flash Memory
DISTINCTIVE CHARACTERISTICS
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Single power supply operation
— 5.0 volt-only operation for read, erase, and
program operations
— Minimizes system level requirements
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Manufactured on 0.35 µm process technology
— Compatible with 0.5 µm Am29F400 device
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High performance
— Access times as fast as 55 ns
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Low power consumption (typical values at 5
MHz)
— 1 µA standby mode current
— 20 mA read current (byte mode)
— 28 mA read current (word mode)
— 30 mA program/erase current
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Flexible sector architecture
— One 16 Kbyte, two 8 Kbyte, one 32 Kbyte, and
seven 64 Kbyte sectors (byte mode)
— One 8 Kword, two 4 Kword, one 16 Kword, and
seven 32 Kword sectors (word mode)
— Supports full chip erase
— Sector Protection features:
A hardware method of locking a sector to
prevent any program or erase operations within
that sector
Sectors can be locked via programming
equipment
Temporary Sector Unprotect feature allows code
changes in previously locked sectors
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Top or bottom boot block configurations
available
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Embedded Algorithms
— Embedded Erase algorithm automatically
preprograms and erases the entire chip or any
combination of designated sectors
— Embedded Program algorithm automatically
writes and verifies data at specified addresses
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Minimum 1,000,000 program/erase cycles per
sector guaranteed
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Package option
— 48-pin TSOP
— 44-pin SO
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Compatibility with JEDEC standards
— Pinout and software compatible with single-
power-supply Flash
— Superior inadvertent write protection
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Data# Polling and toggle bits
— Provides a software method of detecting
program or erase operation completion
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Ready/Busy# pin (RY/BY#)
— Provides a hardware method of detecting
program or erase cycle completion
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Erase Suspend/Erase Resume
— Suspends an erase operation to read data from,
or program data to, a sector that is not being
erased, then resumes the erase operation
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Hardware reset pin (RESET#)
— Hardware method to reset the device to reading
array data
Publication#
21505
Rev:
C
Amendment/+2
Issue Date:
April 1998
PRELIMINARY
GENERAL DESCRIPTION
The Am29F400B is a 4 Mbit, 5.0 volt-only Flash
memory organized as 524,288 bytes or 262,144 words.
The device is offered in 44-pin SO and 48-pin TSOP
packages. The word-wide data (x16) appears on
DQ15–DQ0; the byte-wide (x8) data appears on DQ7–
DQ0. This device is designed to be programmed in-
system with the standard system 5.0 volt V
CC
supply.
A 12.0 V V
PP
is not required for write or erase opera-
tions. The device can also be programmed in standard
EPROM programmers.
This device is manufactured using AMD’s 0.35 µm
process technology, and offers all the features and ben-
efits of the Am29F400, which was manufactured using
0.5 µm process technology.
The standard device offers access times of 55, 60, 70,
90, 120, and 150 ns, allowing high speed microproces-
sors to operate without wait states. To eliminate bus
contention the device has separate chip enable (CE#),
write enable (WE#) and output enable (OE#) controls.
The device requires only a
single 5.0 volt power sup-
ply
for both read and write functions. Internally gener-
ated and regulated voltages are provided for the
program and erase operations.
The device is entirely command set compatible with the
JEDEC single-power-supply Flash standard.
Com-
mands are written to the command register using
standard microprocessor write timings. Register con-
tents serve as input to an internal state-machine that
controls the erase and programming circuitry. Write
cycles also internally latch addresses and data needed
for the programming and erase operations. Reading
data out of the device is similar to reading from other
Flash or EPROM devices.
Device programming occurs by executing the program
command sequence. This initiates the
Embedded
Program
algorithm—an internal algorithm that auto-
matically times the program pulse widths and verifies
proper cell margin.
Device erasure occurs by executing the erase com-
mand sequence. This initiates the
Embedded Erase
algorithm—an internal algorithm that automatically
preprograms the array (if it is not already pro-
grammed) before executing the erase operation. Dur-
ing erase, the device automatically times the erase
pulse widths and verifies proper cell margin.
The host system can detect whether a program or
erase operation is complete by observing the RY/BY#
pin, or by reading the DQ7 (Data# Polling) and
DQ6/DQ2 (toggle)
status bits.
After a program or
erase cycle has been completed, the device is ready to
read array data or accept another command.
The
sector erase architecture
allows memory sectors
to be erased and reprogrammed without affecting the
data contents of other sectors. The device is fully
erased when shipped from the factory.
Hardware data protection
measures include a low
V
CC
detector that automatically inhibits write opera-
tions during power transitions. The
hardware sector
protection
feature disables both program and erase
operations in any combination of the sectors of mem-
ory. This can be achieved via programming equipment.
The
Erase Suspend
feature enables the user to put
erase on hold for any period of time to read data from,
or program data to, any sector that is not selected for
erasure. True background erase can thus be achieved.
The
hardware RESET# pin
terminates any operation
in progress and resets the internal state machine to
reading array data. The RESET# pin may be tied to the
system reset circuitry. A system reset would thus also
reset the device, enabling the system microprocessor
to read the boot-up firmware from the Flash memory.
The system can place the device into the
standby mode.
Power consumption is greatly reduced in this mode.
AMD’s Flash technology combines years of Flash
memory manufacturing experience to produce the
highest levels of quality, reliability and cost effectiveness.
The device electrically erases all bits within a sector
simultaneously via Fowler-Nordheim tunneling. The
data is programmed using hot electron injection.
2
Am29F400B
Making friends through disassembly
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