AM29LV040B_06 datasheet(14/37 Pages) AMD

14 / 37 page

Am29LV040B

21354E4 October 11, 2006

D A TA

SH EE T

DQ7 or DQ6. See “Write Operation Status” for informa-

tion on these status bits.

Any commands written to the device during the

Embedded Program Algorithm are ignored. Note that a

hardware reset immediately terminates the program-

m i ng op erat io n. Th e Byt e Pr ogra m co mm an d

sequence should be reinitiated once the device has

reset to reading array data, to ensure data integrity.

Programming is allowed in any sequence and across

sector boundaries. A bit cannot be programmed

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

the operation and set DQ5 to “1”, or cause the Data#

Polling algorithm to indicate the operation was suc-

cessful. 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

program bytes to the device faster than using the stan-

dard 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 program

command, A0h; the second cycle contains the program

address and data. Additional data is programmed in

the same manner. This mode dispenses with the initial

two unlock cycles required in the standard program

command sequence, resulting in faster total program-

ming time. Table 4 shows the requirements for the

command sequence.

During the unlock bypass mode, only the Unlock

Bypass Program and Unlock Bypass Reset commands

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

must issue the two-cycle unlock bypass reset

command sequence. The first cycle must contain the

data 90h; the second cycle the data 00h. The device

then returns to reading array data.

Figure 1 illustrates the algorithm for the program oper-

ation. See the Erase/Program Operations table in “AC

Characteristics” for parameters, and to Figure 12 for

timing diagrams.

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-

trols or timings during these operations. Table 4 shows

the address and data requirements for the chip erase

command sequence. Note that the autoselect function

is unavailable when an erase operation is in progress.

Any comm ands wr it ten to th e chip dur ing th e

Embedded Erase algorithm are ignored. Note that a

hardware reset during the chip erase operation imme-

diately terminates the operation. The Chip Erase

command sequence should be reinitiated once the

device has returned to reading array data, to ensure

data integrity.

The system can determine the status of the erase oper-

ation by using DQ7, DQ6, or DQ2. See “Write

Operation Status” for information on these status bits.

When the Embedded Erase algorithm is complete, the

device returns to reading array data and addresses are

no longer latched.

Figure 2 illustrates the algorithm for the erase opera-

tion. See the Erase/Program Operations tables in “AC

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 4 for program command sequence.

Figure 1.

Program Operation

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