AM29DL642G datasheet(29/54 Pages) AMD

29 / 54 page

June 10, 2005

Am29DL642G

PRELIMINARY

quence. The Exit SecSi Sector command sequence

returns the device to normal operation. The SecSi

Sector is not accessible when the device is executing

an Embedded Program or embedded Erase algorithm.

Table 13 shows the address and data requirements for

both command sequences. See also “SecSi™ (Se-

cured Silicon) Sector Flash Memory Region” for further

information.

Word Program Command Sequence

Programming is a four-bus-cycle operation. The pro-

gram command 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 al-

gorithm. The system is not required to provide further

controls or timings. The device automatically provides

internally generated program pulses and verifies the

programmed cell margin. Table 13 shows the address

and data requirements for the word 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 words to a bank faster than using the standard

program command sequence. The unlock bypass

command sequence is initiated by first writing two un-

lock cycles. This is followed by a third write cycle con-

taining the unlock bypass command, 20h. That bank

then enters the unlock bypass mode. A two-cycle un-

lock 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 com-

mand, 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 13 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 bank

address and the data 90h. The second cycle need

only contain the data 00h. The bank then returns 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 VHH 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 15 for timing diagrams.

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