AM29LV004 datasheet(12/36 Pages) AMD

12 / 36 page

Am29LV004

PR EL I M I NAR Y

Autoselect Command Sequence

The autoselect command sequence allows the host

system to access the manufacturer and devices codes,

and determine whether or not a sector is protected.

Table 5 shows the address and data requirements.

This method is an alternative to that shown in Table 4,

which is intended for PROM programmers and requires

VID on address bit A9.

The autoselect command sequence is initiated by writ-

ing two unlock cycles, followed by the autoselect com-

mand. The device then enters the autoselect mode,

and the system may read at any address any number

of times, without initiating another command sequence.

A read cycle at address XX00h retrieves the manufac-

turer code. A read cycle at address XX01h returns the

device code. A read cycle containing a sector address

(SA) and the address 02h returns 01h if that sector is

protected, or 00h if it is unprotected. Refer to Tables 2

and 3 for valid sector addresses.

The system must write the reset command to exit the

autoselect mode and return to reading array data.

Byte Program Command Sequence

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

gram command sequence is initiated by writing two un-

lock 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 verify the pro-

grammed cell margin. Table 5 shows the address and

data requirements for the byte program command se-

quence.

When the Embedded Program algorithm is complete,

the device then returns to reading array data 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#. 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 suc-

cessful. However, a succeeding read will show that the

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

to a “1”.

Figure 2 illustrates the algorithm for the program oper-

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

Characteristics” for parameters, and to Figure 14 for

timing diagrams.

Note: See Table 5 for program command sequence.

Figure 2.

Program Operation

START

Write Program

Command Sequence

Data Poll

from System

Verify Data?

Yes

Last Address?

Yes

Programming

Completed

Increment Address

Embedded

Program

algorithm

in progress

21522A-4

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