AM29LV040B_06 datasheet(13/37 Pages) AMD

13 / 37 page

October 11, 2006 21354E4

Am29LV040B

D A TA

SH EE T

COMMAND DEFINITIONS

Writing specific address and data commands or

sequences into the command register initiates device

operations. Table 4 defines the valid register command

sequences. Writing incorrect address and data values

or writing them in the improper sequence may place the

device in an unknown state. A reset command is then

required to return the device to reading array data.

All addresses are latched on the falling edge of WE# or

CE#, whichever happens later. All data is latched on

the rising edge of WE# or CE#, whichever happens

first. Refer to the appropriate timing diagrams in the

“AC Characteristics” section.

Reading Array Data

The device is automatically set to reading array data

after device power-up. No commands are required to

retrieve data. The device is also ready to read array

data after completing an Embedded Program or

Embedded Erase algorithm.

After the device accepts an Erase Suspend command,

the device enters the Erase Suspend mode. The

system can read array data using the standard read

timings, except that if it reads at an address within

erase-suspended sectors, the device outputs status

data. After completing a programming operation in the

Erase Suspend mode, the system may once again

read array data with the same exception. See “Erase

Suspend/Erase Resume Commands” for more infor-

mation on this mode.

The system must issue the reset command to re-

enable the device for reading array data if DQ5 goes

high, or while in the autoselect mode. See the “Reset

Command” section, next.

See also “Requirements for Reading Array Data” in the

“Device Bus Operations” section for more information.

The Read Operations table provides the read parame-

ters, and Figure 11 shows the timing diagram.

Reset Command

Writing the reset command to the device resets the

device to reading array data. Address bits are don’t

care for this command.

The reset command may be written between the

sequence cycles in an erase command sequence

before erasing begins. This resets the device to reading

array data. Once erasure begins, however, the device

ignores reset commands until the operation is

complete.

The reset command may be written between the

sequence cycles in a program command sequence

before programming begins. This resets the device to

reading array data (also applies to programming in

Erase Suspend mode). Once programming begins,

however, the device ignores reset commands until the

operation is complete.

The reset command may be written between the

sequence cycles in an autoselect command sequence.

Once in the autoselect mode, the reset command must

be written to return to reading array data (also applies

to autoselect during Erase Suspend).

If DQ5 goes high during a program or erase operation,

writing the reset command returns the device to

reading array data (also applies dur ing Erase

Suspend).

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 4 shows the address and data requirements. This

method is an alternative to that shown in Table 3, which

is intended for PROM programmers and requires VID

on address bit A9.

The autoselect command sequence is initiated by

writing two unlock cycles, followed by the autoselect

command. 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 00h retrieves the

manufacturer code. A read cycle at address 01h

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 Table 2 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

The byte program command sequence programs one

byte into the device. Programming is a four-bus-cycle

operation. The program command sequence is initi-

ated by writing two unlock write cycles, followed by the

program set-up command. The program address and

data are written next, which in tur n initiate the

Embedded Program algorithm. The system is not

required to provide further controls or timings. The

device automatically provides internally generated

program pulses and verify the programmed cell margin.

Table 4 shows the address and data requirements for

the byte program command sequence. Note that the

autoselect function is unavailable when a program

operation is in progress.

When the Embedded Program algorithm is complete,

the device then returns to reading array data and

addresses are no longer latched. The system can

determine the status of the program operation by using

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