AM29SL400CB100REF datasheet(17/44 Pages) AMD

17 / 44 page

January 23, 2007 Am29SL400C_00_A6

Am29SL400C

D A TA

SH EE T

COMMAND DEFINITIONS

Writing specific address and data commands or sequences

into the command register initiates device operations.

Table 5 on page 18 defines the valid register command se-

quences. Writing incorrect address and data values or

writing them in the improper sequence resets 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 sec-

tion.

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 com-

pleting an Embedded Program or Embedded Erase algo-

rithm.

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 information

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‚ on page 15

section, next.

See also Requirements for Reading Array Data‚ on page 9

for more information. The Read Operations table provides

the read parameters, and Figure 14‚ on page 28 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 com-

mand.

The reset command may be written between the sequence

cycles in an erase command sequence before erasing be-

gins. This resets the device to reading array data. Once era-

sure 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 program-

ming 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 au-

toselect 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, writ-

ing the reset command returns the device to reading 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 deter-

mine whether or not a sector is protected. Table 5 on

page 18 shows the address and data requirements. This

method is an alternative to that shown in Table 4 on page 12,

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 de-

vice 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 manufacturer code. A read cycle at ad-

dress 01h 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) re-

turns 01h if that sector is protected, or 00h if it is unpro-

tected. Refer to Table 2 on page 11 and Table3 on page11

for valid sector addresses.

The system must write the reset command to exit the au-

toselect mode and return to reading array data.

Word/Byte Program Command Sequence

The system may program the device by word or byte, de-

pending on the state of the BYTE# pin. Programming is a

four-bus-cycle operation. The program 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 Pro-

gram algorithm. The system is not required to provide further

controls or timings. The device automatically generates the

program pulses and verifies the programmed cell margin.

Table 5 on page 18 shows the address and data require-

ments for the byte program command sequence.

When the Embedded Program algorithm is complete, the de-

vice then returns to reading array data and addresses are no

longer latched. The system can determine the status of the

program operation by using DQ7, DQ6, or RY/BY#. See

Write Operation Status‚ on page 19 for information on these

status bits.

Any commands written to the device during the Embedded

Program Algorithm are ignored. Note that a hardware reset

immediately terminates the programming operation. The

Byte Program command sequence 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.

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