Autoselect Mode
The autoselect mode provides manufacturer and de-
vice identification, and sector protection verification,
through identifier codes output on DQ7–DQ0. This
mode is primarily intended for programming equipment
to automatically match a device to be programmed with
its corresponding programming algorithm. However,
the autoselect codes can also be accessed in-system
through the command register.
address must appear on the appropriate highest order
address bits. Refer to the corresponding Sector Ad-
dress Tables. The Command Definitions table shows
the remaining address bits that are don’t care. When all
necessary bits have been set as required, the program-
ming equipment may then read the corresponding
identifier code on DQ7–DQ0.
To access the autoselect codes in-system, the host
system can issue the autoselect command via the
command register, as shown in the Command Defini-
tions table. This method does not require VID. See
“Command Definitions” for details on using the autose-
lect mode.
When using programming equipment, the autoselect
mode requires VID (11.5 V to 12.5 V) on address pin
A9. Address pins A6, A1, and A0 must be as shown in
Autoselect Codes (High Voltage Method) table. In addi-
tion, when verifying sector protection, the sector
Table 3. Am29F040B Autoselect Codes (High Voltage Method)
Identifier Code on
DQ7-DQ0
Description
A18–A16 A15–A10 A9 A8–A7 A6 A5–A2 A1
A0
Manufacturer ID: AMD
Device ID: Am29F040B
X
X
X
X
V
X
X
V
X
X
V
V
01h
ID
ID
IL
IL
IL
IL
IL
V
V
V
V
A4h
IH
01h (protected)
00h (unprotected)
Sector Protection
Verification
Sector
Address
X
V
X
V
X
V
V
IL
ID
IL
IH
gramming, which might otherwise be caused by
spurious system level signals during VCC power-up and
power-down transitions, or from system noise.
Sector Protection/Unprotection
The hardware sector protection feature disables both
program and erase operations in any sector. The hard-
ware sector unprotection feature re-enables both
program and erase operations in previously protected
sectors.
Low V
Write Inhibit
CC
When VCC is less than VLKO, the device does not ac-
cept any write cycles. This protects data during VCC
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 VCC
is greater than VLKO. The system must provide the
proper signals to the control pins to prevent uninten-
Sector protection/unprotection must be implemented
using programming equipment. The procedure re-
quires a high voltage (VID) on address pin A9 and the
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.
tional writes when VCC is greater than VLKO
.
Write Pulse “Glitch” Protection
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.
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# =
VIL, CE# = VIH or WE# = VIH. To initiate a write cycle,
CE# and WE# must be a logical zero while OE# is a
logical one.
It is possible to determine whether a sector is protected
or unprotected. See “Autoselect Mode” for details.
Hardware Data Protection
Power-Up Write Inhibit
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-
If WE# = CE# = VIL and OE# = VIH during power up, the
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.
10
Am29F040B
AMD [ AMD ]
