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.
START
If data = 00h,
SecSi Sector is
unprotected.
If data = 01h,
SecSi Sector is
protected.
RESET# =
VIH or VID
Power-Up Write Inhibit
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 automati-
cally reset to the read mode on power-up.
Wait 1 μs
Write 60h to
any address
Remove VIH or VID
from RESET#
COMMON FLASH MEMORY INTERFACE
(CFI)
Write 40h to SecSi
Sector address
with A6 = 0,
Write reset
command
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
families. Flash vendors can standardize their existing
interfaces for long-term compatibility.
A1 = 1, A0 = 0
SecSi Sector
Protect Verify
complete
Read from SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
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 information at the addresses
given in Tables 8–11. To terminate reading CFI data,
the system must write the reset command.The CFI
Query mode is not accessible when the device is exe-
cuting an Embedded Program or embedded Erase al-
gorithm.
Figure 3. Secured Silicon Sector Protect Verify
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadvertent writes (refer to Table 12 for com-
mand definitions). In addition, the following hardware
data protection measures prevent accidental erasure
or programming, which might otherwise be caused by
spurious system level signals during VCC power-up
and power-down transitions, or from system noise.
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 8–11. The
system must write the reset command to reading array
data.
Low VCC Write Inhibit
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 to the read mode. Subsequent
writes are ignored until VCC is greater than VLKO. The
system must provide the proper signals to the control
pins to prevent unintentional writes when VCC is
For further information, please refer to the CFI Specifi-
cation and CFI Publication 100, available via the World
Wide Web at http://www.amd.com/flash/cfi. Alterna-
tively, contact an AMD representative for copies of
these documents.
greater than VLKO
.
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE#, CE#
or WE# do not initiate a write cycle.
June 7, 2005
Am29DL640H
19
SPANSION [ SPANSION ]
