AM29DS320G datasheet(21/54 Pages) SPANSION

21 / 54 page

Am29DS320G

January 27, 2003

AD VA NCE

I N FO RM ATI O N

Figure 3.

SecSi 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 13 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 V

CC 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# =

IL, 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.

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

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 VIH or VID

from RESET#

Write reset

command

SecSi Sector

Protect Verify

complete

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