AM29DL640D datasheet(21/54 Pages) AMD

21 / 54 page

December 13, 2005

Am29DL640D

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.

Low VCC Write Inhibit

When V

CC is less than VLKO, the device does not ac-

cept any write cycles. This protects data during V

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 VLKO. 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 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.

Power-Up Write Inhibit

If WE# = CE# = V

IL 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.

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

families. Flash vendors 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 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

algorithm.

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 return the

device to reading array data.

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.

Write 60h to

any address

Write 40h to SecSi

Sector address

with A6 = 0,

A1 = 1, A0 = 0

START

RESET# =

VIH or VID

Wait 1 ms

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 VIH or VID

from RESET#

Write reset

command

SecSi Sector

Protect Verify

complete

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