AM29LV400BT55RSE データシートの表示（PDF） - Advanced Micro Devices

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AM29LV400BT55RSE

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

COMMAND DEFINITIONS

Writing specific address and data commands or se-

quences into the command register initiates device op-

erations. Table 5 defines the valid register command

sequences. Writing incorrect address and data val-

ues or writing them in the improper sequence may

place the device in an unknown state. A reset com-

mand 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 Em-

bedded Erase algorithm.

After the device accepts an Erase Suspend command,

the device enters the Erase Suspend mode. The sys-

tem can read array data using the standard read tim-

ings, 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-en-

able 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 informa-

tion. The Read Operations table provides the read pa-

rameters, and Figure 13 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 se-

quence cycles in an erase command sequence before

erasing begins. This resets the device to reading array

data. Once erasure begins, however, the device ig-

nores reset commands until the operation is complete.

The reset command may be written between the se-

quence cycles in a program command sequence be-

fore 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 se-

quence 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 read-

ing array data (also applies during 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 pro-

tected. Table 5 shows the address and data require-

ments. 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 se-

quence. A read cycle at address XX00h retrieves the

manufacturer code. A read cycle at address XX01h in

word mode (or 02h in byte mode) returns the device

code. A read cycle containing a sector address (SA)

and the address 02h in word mode (or 04h in byte

mode) returns 01h if that sector is protected, or 00h if

it is unprotected. Refer to Tables 2 and 3 for valid sec-

tor addresses.

The system must write the reset command to exit the

autoselect mode and return to reading array data.

Word/Byte Program Command Sequence

The system may program the device by word or byte,

depending on the state of the BYTE# pin. Program-

ming is a four-bus-cycle operation. The program com-

mand 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 algorithm. The

system is not required to provide further controls or

timings. The device automatically generates the pro-

gram pulses and verifies the programmed cell margin.

Table 5 shows the address and data requirements for

the byte program command sequence.

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

December 4, 2006 21523D4

Am29LV400B

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