BS640HD9V datasheet(42/89 Pages) AMD

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Am29BDS128H/Am29BDS640H

27024B3 May 10, 2006

D A TA

SH EE T

are ignored. Another Erase Suspend command can be

written after the chip has resumed erasing.

Figure 5.

Erase Operation

Password Program Command

The Password Program Command permits program-

ming the password that is used as part of the hard-

ware protection scheme. The actual password is

64-bits long. 4 Password Program commands are re-

quired to program the password. The user must enter

the unlock cycle, password program command (38h)

and the program address/data for each portion of the

password when programming. There are no provisions

for entering the 2-cycle unlock cycle, the password

program command, and all the password data. There

is no special addressing order required for program-

ming the password. Also, when the password is under-

going programming, Simultaneous Operation is

disabled. Read operations to any memory location will

return the programming status. Once programming is

complete, the user must issue a Read/Reset com-

mand to return the device to normal operation. Once

the Password is written and verified, the Password

Mode Locking Bit must be set in order to prevent verifi-

cation. The Password Program Command is only ca-

pable of programming “0”s. Programming a “1” after a

cell is programmed as a “0” results in a time-out by the

Embedded Program Algorithm™ with the cell remain-

ing as a “0”. The password is all Fs when shipped from

the factory. All 64-bit password combinations are valid

as a password.

Password Verify Command

The Password Verify Command is used to verify the

Password. The Password is verifiable only when the

Password Mode Locking Bit is not programmed. If the

Password Mode Locking Bit is programmed and the

user attempts to verify the Password, the device will al-

ways drive all Fs onto the DQ data bus.

Also, the device will not operate in Simultaneous Oper-

ation when the Password Verify command is executed.

Only the password is returned regardless of the bank

address. The lower two address bits (A1–A0) are valid

during the Password Verify. Writing the SecSi Sector

Exit command returns the device back to normal oper-

ation.

Password Protection Mode Locking Bit

Program Command

The Password Protection Mode Locking Bit Program

Command programs the Password Protection Mode

Locking Bit, which prevents further verifies or updates

to the password. Once programmed, the Password

Protection Mode Locking Bit cannot be erased and the

Persistent Protection Mode Locking Bit program cir-

cuitry is disabled, thereby forcing the device to remain

in the Password Protection Mode. After issuing

“PL/68h” at the fourth bus cycle, the device requires a

time out period of approximately 150 µs for program-

ming the Password Protection Mode Locking Bit. Then

by writing “PL/48h” at the fifth bus cycle, the device

outputs verify data at DQ0. If DQ0 = 1, then the Pass-

word Protection Mode Locking Bit is programmed. If

not, the system must repeat this program sequence

from the fourth cycle of “PL/68h”. Exiting the Password

Protection Mode Locking Bit Program command is ac-

complished by writing the SecSi Sector Exit command

or Read/Reset command.

Persistent Sector Protection Mode

Locking Bit Program Command

The Persistent Sector Protection Mode Locking Bit

Program Command programs the Persistent Sector

Protection Mode Locking Bit, which prevents the Pass-

word Mode Locking Bit from ever being programmed.

By disabling the program circuitry of the Password

Mode Locking Bit, the device is forced to remain in the

Persistent Sector Protection mode of operation, once

this bit is set. After issuing “SMPL/68h” at the fourth

bus cycle, the device requires a time out period of ap-

proximately 150 µs for programming the Persistent

Prote c tion Mo de L o ck in g Bit. T hen by wr itin g

“SMPL/48h” at the fifth bus cycle, the device outputs

verify data at DQ0. If DQ0 = 1, then the Persistent Pro-

START

Write Erase

Command Sequence

Data Poll

from System

Data = FFh?

Yes

Erasure Completed

Embedded

Erase

algorithm

in progress

Notes:

1. See Table 20 for erase command sequence.

2. See the section on DQ3 for information on the sector

erase timer.

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