AM29PDL640G datasheet(24/61 Pages) SPANSION

24 / 61 page

February 26, 2003

Am29PDL640G

P R E L I M INARY

but can be programmed and locked only once. Note

that the accelerated programming (ACC) and unlock

bypass functions are not available when programming

the SecSi Sector.

The SecSi Sector area can be protected using one of

the following procedures:

■ Write the three-cycle Enter SecSi Sector Region

command sequence, and then follow the in-system

sector protect algorithm as shown in Figure Note:,

except that RESET# may be at either V

IH or VID.

This allows in-system protection of the SecSi Sector

Region without raising any device pin to a high volt-

age. Note that this method is only applicable to the

SecSi Sector.

■ To verify the protect/unprotect status of the SecSi

Sector, follow the algorithm shown in Figure 3.

Once the SecSi Sector is locked and verified, the sys-

tem must write the Exit SecSi Sector Region com-

mand sequence to return to reading and writing the

remainder of the array.

The SecSi Sector lock must be used with caution

since, once locked, there is no procedure available for

unlocking the SecSi Sector area and none of the bits

in the SecSi Sector memory space can be modified in

any way.

SecSi Sector Protection Bit

The SecSi Sector Protection Bit prevents program-

ming of the SecSi Sector memory area. Once set, the

SecSi Sector memory area contents are non-modifi-

able.

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. 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

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, any time the device is ready to read array data.

The system can read CFI information at the addresses

given in Tables 10–13. To terminate reading CFI data,

the system must write the reset command. The CFI

Query mode is not accessible when the device is exe-

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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