AM29DL800B datasheet(16/43 Pages) AMD

16 / 43 page

Am29DL800B

P R E L I M I NARY

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 pin A9. The autoselect command sequence

may be written to an address within a bank that is either

in the read or erase-suspend-read mode. The autose-

lect command may not be written while the device is

actively programming 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 au-

toselect command. The addressed bank then enters

the autoselect mode. The system may read at any ad-

dress within the same bank any number of times with-

out initiating another autoselect command sequence:

s A read cycle at address (BA)XX00h (where BA is

the bank address) returns the manufacturer code.

s A read cycle at address (BA)XX01h in word mode

(or (BA)XX02h in byte mode) returns the device

code.

s A read cycle to an address containing a sector ad-

dress (SA) within the same bank, and the address

02h on A7–A0 in word mode (or the address 04h on

A6–A-1 in byte mode) returns 01h if the sector is

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

2 and 3 for valid sector addresses.

The system may continue to read array data from the

other bank while a bank is in the autoselect mode. To

exit the autoselect mode, the system must write the

reset command to return both banks to reading array

data. If a bank enters the autoselect mode while erase

suspended, a reset command returns that bank to the

erase-suspend-read mode. A subsequent Erase

Resume command returns the bank to the erase oper-

ation.

Byte/Word 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 tim-

ings. The device automatically generates the program

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,

that bank 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#. Note that while the Embedded Pro-

gram operation is in progress, the system can read

data from the non-programming bank. Refer to the

Write Operation Status section 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

operation. The program command sequence should be

reinitiated once that bank has returned to reading array

data, to ensure data integrity.

Programming is allowed in any sequence and across

sector boundaries. A bit cannot be programmed

from “0” back to a “1.” Attempting to do so may cause

that bank to set DQ5 = 1, or cause the DQ7 and DQ6

status bits 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.”

Unlock Bypass Command Sequence

The unlock bypass feature allows the system to pro-

gram bytes or words to a bank faster than using the

standard program command sequence. The unlock by-

pass command sequence is initiated by first writing two

unlock cycles. This is followed by a third write cycle

containing the unlock bypass command, 20h. That

bank then enters the unlock bypass mode. A two-cycle

unlock bypass program command sequence is all that

is required to program in this mode. The first cycle in

this sequence contains the unlock bypass program

command, A0h; the second cycle contains the program

address and data. Additional data is programmed in

the same manner. This mode dispenses with the initial

two unlock cycles required in the standard program

command sequence, resulting in faster total program-

ming time. Table 5 shows the requirements for the com-

mand sequence.

During the unlock bypass mode, only the Unlock Bypass

Program and Unlock Bypass Reset commands are

valid. To exit the unlock bypass mode, the system must

issue the two-cycle unlock bypass reset command se-

quence. The first cycle must contain the bank address

and the data 90h. The second cycle need only contain

the data 00h. The bank then returns to reading array

data.

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