D A T A S H E E T
against inadvertent writes (refer to Table 14 for com-
COMMON FLASH MEMORY INTERFACE
(CFI)
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 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.
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 reading array data. Subse-
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 sys-
tem can read CFI information at the addresses given
in Tables 10–13. To terminate reading CFI data, the
system must write the reset command.
quent 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 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.
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 10–13. The
system must write the reset command to return the
device to the autoselect mode.
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.
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/products/nvd/over-
view/cfi.html. Alternatively, contact an AMD
representative for copies of these documents.
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 reading array data on power-up.
Table 10. CFI Query Identification String
Addresses
Addresses
(Word Mode)
(Byte Mode)
Data
Description
10h
11h
12h
20h
22h
24h
0051h
0052h
0059h
Query Unique ASCII string “QRY”
13h
14h
26h
28h
0002h
0000h
Primary OEM Command Set
15h
16h
2Ah
2Ch
0040h
0000h
Address for Primary Extended Table
17h
18h
2Eh
30h
0000h
0000h
Alternate OEM Command Set (00h = none exists)
Address for Alternate OEM Extended Table (00h = none exists)
19h
1Ah
32h
34h
0000h
0000h
22
Am29DL16xD
21533E6 February 26, 2009
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