AM29F040B-1 Advanced Micro Devices, AM29F040B-1 Datasheet - Page 8

• Manufacturer Part Number: AM29F040B-1
• Description: 4 Megabit (512 K x 8-Bit) CMOS 5.0 Volt-only/ Uniform Sector Flash Memory
• Manufacturer: Advanced Micro Devices

Sector Protection/Unprotection
The hardware sector protection feature disables both
program and erase operations in any sector. The
hardware sector unprotection feature re-enables both
program and erase operations in previously pro-
tected sectors.
Sector protection/unprotection must be implemented
using programming equipment. The procedure re-
quires a high voltage (V
control pins. Details on this method are provided in a
supplement, publication number 19957. Contact an
AMD representative to obtain a copy of the appropriate
document.
The device is shipped with all sectors unprotected.
AMD offers the option of programming and protecting
sectors at its factory prior to shipping the device
through AMD’s ExpressFlash™ Service. Contact an
AMD representative for details.
It is possible to determine whether a sector is protected
or unprotected. See “Autoselect Mode” for details.
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadvertent writes (refer to the Command Defi-
nitions table). In addition, the following hardware data
protection measures prevent accidental erasure or pro-
COMMAND DEFINITIONS
Writing specific address and data commands or se-
quences into the command register initiates device op-
erations. The Command Definitions table defines the
valid register command sequences. Writing incorrect
address and data values or writing them in the im-
proper sequence resets the device to reading array
data.
All addresses are latched on the falling edge of WE# or
CE#, whichever happens later. All data is latched on
the rising edge of WE# or CE#, whichever happens
first. Refer to the appropriate timing diagrams in the
“AC Characteristics” section.
8
Manufacturer ID: AMD
Device ID: Am29F040B
Sector Protection
Verification
Description
Table 3. Am29F040B Autoselect Codes (High Voltage Method)
ID
) on address pin A9 and the
A18–A16
Address
Sector
X
X
A15–A10
X
X
X
P R E L I M I N A R Y
V
V
V
A9
ID
ID
ID
Am29F040B
A8–A7
X
X
X
gramming, which might otherwise be caused by spuri-
ous system level signals during V
power-down transitions, or from system noise.
Low V
When V
cept any write cycles. This protects data during V
power-up and power-down. The command register and
all internal program/erase circuits are disabled, and the
device resets. Subsequent writes are ignored until V
is greater than V
proper signals to the control pins to prevent uninten-
tional writes when V
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE#, CE# or
WE# do not initiate a write cycle.
Logical Inhibit
Write cycles are inhibited by holding any one of OE# =
V
CE# and WE# must be a logical zero while OE# is a
logical one.
Power-Up Write Inhibit
If WE# = CE# = V
device does not accept commands on the rising edge
of WE#. The internal state machine is automatically
reset to reading array data on power-up.
Reading Array Data
The device is automatically set to reading array data
after device power-up. No commands are required to
retrieve data. The device is also ready to read array
data after completing an Embedded Program or Em-
bedded Erase algorithm.
After the device accepts an Erase Suspend command,
the device enters the Erase Suspend mode. The sys-
tem can read array data using the standard read tim-
ings, except that if it reads at an address within erase-
suspended sectors, the device outputs status data.
After completing a programming operation in the Erase
Suspend mode, the system may once again read array
IL
, CE# = V
V
V
V
A6
IL
IL
IL
CC
CC
A5–A2
Write Inhibit
X
X
X
is less than V
IH
or WE# = V
IL
V
V
V
A1
LKO
IH
IL
IL
and OE# = V
CC
. The system must provide the
is greater than V
V
V
V
A0
IH
IL
IL
LKO
IH
, the device does not ac-
. To initiate a write cycle,
IH
Identifier Code on
00h (unprotected)
during power up, the
01h (protected)
CC
DQ7-DQ0
A4h
01h
power-up and
LKO
.
CC
CC