Am29DL320G 21
Figure 3. SecSi Sector Protect Verify
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadver tent wr ites (refer to Table 13 for c om -
mand definitions) . In addition, the follow ing hardware
data protection measures prevent accidental erasure
or programming, which might otherwise be caused by
spurious system level signals during V
CC
power-up
and power-down transitions, or from system noise.
Low V
CC
Write Inhibit
When V
CC
is less than V
LKO
, the device does not ac-
cept any write cycles. This protects data during V
CC
power-up and power-down. The command register
and all internal program/erase circuits are disabled,
and the device resets to the read mode. Subsequent
writes are ignored until V
CC
is greater than V
LKO
. The
system must provide the proper signals to the control
pins to prevent unintentional writes when V
CC
is
greater than V
LKO
.
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 an y one of OE# =
V
IL
, CE# = V
IH
or WE# = V
IH
. To initiate a wr ite cycle,
CE# and WE# must be a logical zero while OE# is a
logical one.
Power-Up Write Inhibit
If WE# = CE# = V
IL
and OE# = V
IH
during power up,
the device does not accept commands on the rising
edge of WE#. The in terna l state machine is au tomati-
cally reset to the read mode on power- up.
COMMON FLASH MEMORY INTERFACE
(CFI)
The Common Flash Interface (CFI) specification out-
lines device and host system software interrogation
handshake, which allows specific vendor-specified
software algorithms to be used for entire families of
devices. Software support can then be device-inde-
pendent, JEDEC ID-independent, and forward- and
backward-compatible for the specified flash device
fam ilies. Flash vend ors can standardize their existing
interfaces for long-term compatibility.
This device enters the CFI Query mode when the sys-
tem writes the CFI Query command, 98h, to address
55h in word mode (or address AAh in byte mode), any
time the device is ready to read array data. The
system can read CFI infor mation at the addresses
given in Tables 9–12. To ter minate reading CFI data,
the system must write the reset command. The CFI
Quer y mode is not accessible when the device is exe-
cuting an Embedded Program or Embedded Erase al-
gorithm.
The system can also write the CFI query command
when the device is in the autoselect mode. The device
enters the CFI query mode, and the system can read
CFI data at the addresses given in Tables 9–12 . The
system must write the reset command to retur n the
device to reading array data.
For further information, please refer to the CFI Specifi-
cation and CFI Pub licat ion 100, a v ail ab le via the World
Wide Web at http://www.amd.com/flash/cfi. Alterna-
tively, contact an AMD representative for copies of
these documents.
Write 60h to
any address
Write 40h to SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
START
RESET# =
V
IH
or V
ID
Wait 1 μs
Read from SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
If data = 00h,
SecSi Sector is
unprotected.
If data = 01h,
SecSi Sector is
protected.
Remove V
IH
or V
ID
from RESET#
Write reset
command
SecSi Sector
Protect Verify
complete
