22 Am49DL640BG March 8, 2002
PRELIMINARY
power-up and power-down. The command register
and all internal program/erase circuits are disabled,
and t he devi ce r ese ts to the rea d mo de . Sub seq uent
writes are ig nored unti l V
CC
is greate r than V
LKO
. The
system m ust prov ide the pr oper sig nals to t he contr ol
pins to prevent unintentional writes when V
CC
is
greater than V
LKO
.
Write Pulse “Glitch” Protectio n
Noise pulses of less than 5 ns (typical) on O E#, CE#f
or WE# do not initiate a write cycle.
Logical Inhibit
Write cycles are inhibited by holding any one of OE# =
V
IL
, CE #f = V
IH
or WE# = V
IH
. To initiate a write cycle,
CE#f a nd W E# m ust be a logic al ze ro whil e OE# is a
logical one.
Power-Up Writ e Inhibit
If WE # = C E#f = V
IL
and OE# = V
IH
dur ing po wer u p,
the device does not accept commands on the rising
edge of WE #. The internal state m achine is automat i-
call y 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-in dependent, and forw ard- and
bac kward-compatible for the spec ified fl ash device
familie s. Fla sh ven dors can standar dize the ir exis ting
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 addr ess 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.
The system can als o write the CFI qu ery command
when the device is in the autoselect mode. The device
ent ers the CFI qu ery mode , and the syst em ca n read
CFI data at the addresses given in Tables 8–11. The
system must write the reset c ommand to return the de-
vice to the autoselect mode.
For further information, pleas e refer to the CFI Specifi-
cation and CFI Publication 100, available via the
World Wide Web at http://www.amd.com/prod-
ucts/n vd/overview/cfi.html. Alternatively, c ontact an
AMD representative for copies of these documents.
Table 8. CFI Query Identification String
Add resses
(Word Mode)
Addr esses
(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
Add ress for Primary Extended Table
17h
18h
2Eh
30h
0000h
0000h
Alternate OEM Command Set (00h = none exists)
19h
1Ah
32h
34h
0000h
0000h
Add res s for Alternate OEM Extended Table (00h = none exists)
