AM29DS323D datasheet(25/54 Pages) AMD

25 / 54 page

Am29DS323D

P R E L I M I NARY

COMMAND DEFINITIONS

Writing specific address and data commands or se-

quences into the command register initiates device

operations. Table 14 defines the valid register com-

mand sequences. Writing incorrect address and

data values or writing them in the improper se-

quence 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 AC Characteristics section for timing

diagrams.

Reading Array Data

The device is automatically set to reading array data

after device power-up. No commands are required to

retrieve data. Each bank is ready to read array data

after completing an Embedded Program or Embedded

Erase algorithm.

After the device accepts an Erase Suspend command,

the co rres ponding ban k enters the eras e-su s -

pend-read mode, after which the system can read

data from any non-erase-suspended sector within the

same bank. After completing a programming operation

in the Erase Suspend mode, the system may once

again read array data with the same exception. See

the Erase Suspend/Erase Resume Commands sec-

tion for more information.

The system

must issue the reset command to return a

bank to the read (or erase-suspend-read) mode if DQ5

goes high during an active program or erase opera-

tion, or if the bank is in the autoselect mode. See the

next section, Reset Command, for more information.

See also Requirements for Reading Array Data in the

Device Bus Operations section for more information.

The Memory Array Read-Only Operations table pro-

vides the read parameters, and Figure 13 shows the

timing diagram.

Reset Command

Writing the reset command resets the banks to the

read or erase-suspend-read mode. Address bits are

don’t cares 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 bank to which the sys-

tem was writing 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 bank to

which the system was writing to reading array data. If

the program command sequence is written to a bank

that is in the Erase Suspend mode, writing the reset

c o mma nd re t u r n s t hat b a n k t o t h e eras e - s u s -

pend-read 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. If a

bank entered the autoselect mode while in the Erase

Suspend mode, writing the reset command returns

that bank to the erase-suspend-read mode.

If DQ5 goes high during a program or erase operation,

writing the reset command returns the banks to read-

ing array data (or erase-suspend-read mode if that

bank was in Erase Suspend).

Autoselect Command Sequence

The autoselect command sequence allows the host

system to access the manufacturer and device codes,

and determine whether or not a sector is protected.

Table 14 shows the address and data requirements.

This method is an alternative to that shown in Table 7,

which is intended for PROM programmers and re-

qu ire s V

ID o n a ddr es s pi n A 9 . T h e au tos e l e c t

command sequence may be written to an address

w i t h in a bank t h a t is eit her in t he read or

erase-suspend-read mode. The autoselect command

may not be written while the device is actively pro-

gramming or erasing in the other bank.

The autoselect command sequence is initiated by first

writing two unlock cycles. This is followed by a third

write cycle that contains the bank address and the

autoselect command. The bank then enters the

autoselect mode. The system may read at any address

within the same bank any number of times without ini-

tiating another autoselect command sequence. The fol-

lowing table describes the hex address requirements

for the various autoselect functions, and the resulting

data. BA represents the bank address, and SA repre-

sents the sector address.

* For byte mode, ignore data output bits D8–DQ15.

Description

Word

Address

Byte

Address

Read Data*

Maufacturer ID

(BA) + 00

Device ID

(BA) + 01

(BA) + 02

22B7 (top boot)

22B8 (bottom boot)

Sector Block

Protect Verify

(SA) + 02

(SA) + 04

00 (unlocked),

01 (locked)

SecSi Sector

Factory

Protect

(BA) + 03

(BA) + 06

85 (factory locked)

05 (not factory locked)

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