AM29BDD160G datasheet(44/79 Pages) AMD

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Am29BDD160G

June 7, 2006

Verify. Writing the Read/Reset command returns the

device back to normal operation.

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! If the

Password Protection Mode Locking Bit is verified as

program without margin, the Password Protection

Mode Locking Bit Program command can be executed

to improve the program margin. Once the Password

Protection Mode Locking Bit is programmed, the Per-

sistent Sector Protection Locking Bit program circuitry

is disabled, thereby forcing the device to remain in the

Password Protection mode. Exiting the Mode Locking

Bit Program command is accomplished by writing the

Read/Reset command.

The Password Protection Mode Locking Bit Program

command is permitted if the SecSi sector is enabled.

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.

If the Persistent Sector Protection Mode Locking Bit is

verified as programmed without margin, the Persistent

Sector Protection Mode Locking Bit Program Com-

mand should be reissued to improve program margin.

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. Exiting the Persistent Protection Mode

Locking Bit Program command is accomplished by

writing the Read/Reset command.

The Persistent Sector Protection Mode Locking Bit

Program command is permitted if the SecSi sector is

enabled.

SecSi Sector Protection Bit Program

Command

The SecSi Sector Protection Bit Program Command

programs the SecSi Sector Protection Bit, which pre-

vents the SecSi sector memory from being cleared. If

the SecSi Sector Protection Bit is verified as pro-

grammed without margin, the SecSi Sector Protection

Bit Program Command should be reissued to improve

program margin. Exiting the VCC-level SecSi Sector

Protection Bit Program Command is accomplished by

writing the Read/Reset command.

The SecSi Sector Protection Bit Program command is

permitted if the SecSi sector is enabled.

PPB Lock Bit Set Command

The PPB Lock Bit Set command is used to set the

PPB Lock bit if it is cleared either at reset or if the

Password Unlock command was successfully exe-

cuted. There is no PPB Lock Bit Clear command.

Once the PPB Lock Bit is set, it cannot be cleared un-

less the device is taken through a power-on clear or

the Password Unlock command is executed. Upon

setting the PPB Lock Bit, the PPBs are latched into the

DYBs. If the Password Mode Locking Bit is set, the

PPB Lock Bit status is reflected as set, even after a

power-on reset cycle. Exiting the PPB Lock Bit Set

command is accomplished by writing the Read/Reset

command.

The PPB Lock Bit Set command is permitted if the

SecSi sector is enabled.

DYB Write Command

The DYB Write command is used to set or clear a DYB

for a given sector. The high order address bits

(A18–A11) are issued at the same time as the code

01h or 00h on DQ7-DQ0. All other DQ data bus pins

are ignored during the data write cycle. The DYBs are

modifiable at any time, regardless of the state of the

PPB or PPB Lock Bit. The DYBs are cleared at

power-up or hardware reset.Exiting the DYB Write

command is accomplished by writing the Read/Reset

command.

The DYB Write command is permitted if the SecSi

sector is enabled.

Password Unlock Command

The Password Unlock command is used to clear the

PPB Lock Bit so that the PPBs can be unlocked for

modification, thereby allowing the PPBs to become ac-

cessible for modification. The exact password must be

entered in order for the unlocking function to occur.

This command cannot be issued any faster than 2 µs

at a time to prevent a hacker from running through the

all 64-bit combinations in an attempt to correctly match

a password. If the command is issued before the 2 µs

execution window for each portion of the unlock, the

command will be ignored.

The Password Unlock function is accomplished by

writing Password Unlock command and data to the

device to perform the clearing of the PPB Lock Bit.

The password is 64 bits long, so the user must write

the Password Unlock command 2 times for a x32 bit

data bus and 4 times for a x16 data bus. A0 is used to

determine whether the 32 bit data quantity is used to

match the upper 32 bits or lower 32 bits. A0 and A-1 is

used for matching when the x16 bit data bus is se-

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