L320DB90VC datasheet(28/57 Pages) AMD

28 / 57 page

Am29LV320D

December 14, 2005

DA TA SH EET

icon sector command sequence. The Exit Secured Sil-

icon sector command sequence returns the device to

normal operation. Table 14 on page 29 shows the ad-

dress and data requirements for both command se-

quences. Note that the ACC function and unlock

bypass modes are not available when the device en-

ters the Secured Silicon sector. See also “Secured Sil-

icon Sector Flash Memory Region” on page 20 for

further information.

Byte/Word Program Command Sequence

The system may program the device by word or byte,

depending on the state of the BYTE# pin. Program-

ming is a four-bus-cycle operation. The program com-

mand sequence is initiated by writing two unlock write

cycles, followed by the program set-up command. The

program address and data are written next, which in

turn initiate the Embedded Program algorithm. The

system is not required to provide further controls or

timings. The device automatically provides internally

generated program pulses and verifies the pro-

grammed cell margin. Table 14 on page 29 shows the

address and data requirements for the byte program

command sequence. Note that the autoselect, Se-

cured Silicon sector, and CFI modes are unavailable

while a programming operation is in progress.

When the Embedded Program algorithm is complete,

the device then returns to the read mode and ad-

dresses are no longer latched. The system can deter-

mine the status of the program operation by using

DQ7, DQ6, or RY/BY#. Refer to “Write Operation Sta-

tus” on page 30 for information on these status bits.

Any commands written to the device during the Em-

bedded Program Algorithm are ignored. Note that a

hardware reset immediately terminates the program

operation. The program command sequence should

be reinitiated once the device returns to the read

mode, to ensure data integrity.

Programming is allowed in any sequence and across

sector boundaries. A bit cannot be programmed

from “0” back to a “1.” Attempting to do so may

cause the device to set DQ5 = 1, or cause the DQ7

and DQ6 status bits to indicate the operation was suc-

cessful. However, a succeeding read shows that the

data is still “0.” Only erase operations can convert a “0”

to a “1.”

Unlock Bypass Command Sequence

The unlock bypass feature allows the system to pro-

gram bytes or words to the device faster than using the

standard program command sequence. The unlock

bypass command sequence is initiated by first writing

two unlock cycles. This is followed by a third write

cycle containing the unlock bypass command, 20h.

The device then enters the unlock bypass mode. A

two-cycle unlock bypass program command sequence

is all that is required to program in this mode. The first

cycle in this sequence contains the unlock bypass pro-

gram command, A0h; the second cycle contains the

program address and data. Additional data is pro-

grammed in the same manner. This mode dispenses

with the initial two unlock cycles required in the stan-

dard program command sequence, resulting in faster

total programming time. Table 14 on page 29 shows

the requirements for the command sequence.

During the unlock bypass mode, only the Unlock By-

pass Program and Unlock Bypass Reset commands

are valid. To exit the unlock bypass mode, the system

must issue the two-cycle unlock bypass reset com-

mand sequence. The first cycle must contain the data

90h. The second cycle need only contain the data 00h.

The device then re turns to the read mode.

The device offers accelerated program operations

through the WP#/ACC pin. When the system asserts

VHH on the WP#/ACC pin, the device automatically en-

ters the Unlock Bypass mode. The system may then

write the two-cycle Unlock Bypass program command

sequence. The device uses the higher voltage on the

WP#/ACC pin to accelerate the operation. Note that

the WP#/ACC pin must not be at V

HH any operation

other than accelerated programming, or device dam-

age may result. In addition, the WP#/ACC pin must not

be left floating or unconnected; inconsistent behavior

of the device may result.

Figure 4, on page 27 illustrates the algorithm for the

program operation. Refer to the table “Erase and Pro-

gram Operations” on page 41 for parameters, and Fig-

ure 18, on page 42 for timing diagrams.

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