AM29DL322D datasheet(25/54 Pages) AMD

25 / 54 page

Am29DL322D/323D/324D

June 10, 2003

grammed cell margin. Table 14 shows the address

and data requirements for the byte program command

sequence.

When the Embedded Program algorithm is complete,

that bank 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 the Write Operation

Status section 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 that bank has returned 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 that bank to set DQ5 = 1, or cause the DQ7 and

DQ6 status bits to indicate the operation was success-

ful. However, a succeeding read will show 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 a bank 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.

That bank 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 shows the require-

ments 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. See Table 14 for address and data

requirements.

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 3 illustrates the algorithm for the program oper-

ation. Refer to the Erase and Program Operations

table in the AC Characteristics section for parameters,

and Figure 17 for timing diagrams.

Figure 3.

Program Operation

Chip Erase Command Sequence

Chip erase is a six bus cycle operation. The chip erase

command sequence is initiated by writing two unlock

cycles, followed by a set-up command. Two additional

unlock write cycles are then followed by the chip erase

command, which in turn invokes the Embedded Erase

algorithm. The device does not require the system to

preprogram prior to erase. The Embedded Erase algo-

rithm automatically preprograms and verifies the entire

memory for an all zero data pattern prior to electrical

erase. The system is not required to provide any con-

START

Write Program

Command Sequence

Data Poll

from System

Verify Data?

Yes

Last Address?

Yes

Programming

Completed

Increment Address

Embedded

Program

algorithm

in progress

Note: See Table 14 for program command sequence.

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