S29AL032D datasheet(29/69 Pages) SPANSION

29 / 69 page

June 13, 2005 S29AL032D_00_A3

S29AL032D

Ad vance

Info rmat i o n

without raising any device pin to a high voltage. Note that this method is only applicable to

the Secured Silicon Sector.

To verify the protect/unprotect status of the Secured Silicon Sector, follow the algorithm

shown in Figure 3, on page 27.

Once the Secured Silicon Sector is locked and verified, the system must write the Exit Secured

Silicon Sector Region command sequence to return to reading and writing the remainder of the

array.

The Secured Silicon Sector protection must be used with caution since, once protected, there is

no procedure available for unprotecting the Secured Silicon Sector area and none of the bits in

the Secured Silicon Sector memory space can be modified in any way.

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 17 on page 38 for command definitions). In

addition, the following hardware data protection measures prevent accidental erasure or pro-

gramming, 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 VCC is less than VLKO, the device does not accept 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. 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 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.

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.

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

S29AL032D Datasheet(PDF) 29 Page - SPANSION

S29AL032D Datasheet(HTML) 29 Page - SPANSION

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