AM29LV400BB55RSE データシートの表示（PDF） - Advanced Micro Devices

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AM29LV400BB55RSE

4 Megabit (512 K x 8-Bit/256 K x 16-Bit) CMOS 3.0 Volt-only Boot Sector Flash Memory

Advanced Micro Devices 

DATA SHEET

DQ7, DQ6, or RY/BY#. See “Write Operation Status”

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-

ming operation. The Byte Program command se-

quence 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

successful. 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 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 5 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. The first cycle must contain the pro-

gram address and the data 90h. The second cycle

need only contain the data 00h. The device then re-

turns to reading array data.

Figure 3 illustrates the algorithm for the program oper-

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

Characteristics” for parameters, and to Figure 17 for

timing diagrams.

START

Write Program

Command Sequence

Embedded

Program

algorithm

in progress

Data Poll

from System

Verify Data?

No

Yes

Increment Address

No

Last Address?

Yes

Programming

Completed

Note: See Table 5 for program command sequence.

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-

trols or timings during these operations. Table 5 shows

the address and data requirements for the chip erase

command sequence.

Any commands written to the chip during the Embed-

ded Erase algorithm are ignored. Note that a hard-

ware reset during the chip erase operation

immediately terminates the operation. The Chip Erase

command sequence should be reinitiated once the de-

16

Am29LV400B

21523D4 December 4, 2006

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