AM29PDL128G35PEFN datasheet(41/71 Pages) AMD

41 / 71 page

Am29PDL128G

October 28, 2004

P R E L IM IN A R Y

DYB Write Command

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

for a given sector. The high order address bits

(A21–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 sec-

tor 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 is ignored.

The Password Unlock function is accomplished by

writing Password Unlock command and data to the de-

vice 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.

Once the Password Unlock command is entered, the

RY/BY# pin goes LOW indicating that the device is

busy. Approximately 2 µs is required for each portion

of the unlock. Once the first portion of the password

unlock completes (RY/BY# is not driven and DQ6 does

not toggle when read), the Password Unlock com-

mand is issued again, only this time with the next part

of the password. If WORD# = 1, the second Password

Unlock command is the final command before the PPB

Lock Bit is cleared (assuming a valid password). If

WORD# = 0, this is the fourth Password Unlock com-

mand. In x16 mode, four Password Unlock commands

are required to successfully clear the PPB Lock Bit. As

with the first Password Unlock command, the RY/BY#

signal goes LOW and reading the device results in the

DQ6 pin toggling on successive read operations until

complete. It is the responsibility of the microprocessor

to keep track of the number of Password Unlock com-

mands (2 for x32 bus and 4 for x16 bus), the order,

and when to read the PPB Lock bit to confirm suc-

cessful password unlock

The Password Unlock command is permitted if the

SecSi sector is enabled.

PPB Program Command

The PPB Program command is used to program, or

set, a given PPB. Each PPB is individually pro-

grammed (but is bulk erased with the other PPBs).

The specific sector address (A21–A11) are written at

the same time as the program command 60h with A6

= 0. If the PPB Lock Bit is set and the corresponding

PPB is set for the sector, the PPB Program command

does not execute and the command times-out without

programming the PPB.

After programming a PPB, two additional cycles are

needed to determine whether the PPB has been pro-

grammed with margin. If the PPB has been pro-

grammed without margin, the program command

should be reissued to improve the program margin.

The PPB Program command is permitted if the SecSi

sector is enabled. The PPB Program command does

not follow the Embedded Program algorithm.

All PPB Erase Command

The All PPB Erase command is used to erase all

PPBs in bulk. There is no means for individually eras-

ing a specific PPB. Unlike the PPB program, no spe-

cific sector address is required. However, when the

PPB erase command is written (60h) and A6 = 1, all

Sector PPBs are erased in parallel. If the PPB Lock Bit

is set, the ALL PPB Erase command does not execute

and the command times-out without erasing the PPBs.

After erasing the PPBs, two additional cycles are

needed to determine whether the PPB has been

erased with margin. If the PPBs has been erased with-

out margin, the erase command should be reissued to

improve the program margin.

It is the responsibility of the user to preprogram all

PPBs prior to issuing the All PPB Erase command. If

the user attempts to erase a cleared PPB, over-era-

sure may occur making it difficult to program the PPB

at a later time. Note: The total number of PPB pro-

gram/erase cycles is limited to 100 cycles. Cycling the

PPBs beyond 100 cycles is not guaranteed.

The All PPB Erase command is permitted if the SecSi

sector is enabled.

DYB Write Command

The DYB Write command is used for setting the DYB,

which is a volatile bit that is cleared at hardware reset.

There is one DYB per sector. If the PPB is set, the sec-

tor is protected regardless of the value of the DYB. If

the PPB is cleared, setting the DYB to a 1 protects the

sector from programs or erases. Since this is a volatile

bit, removing power or resetting the device clears the

DYBs. The bank address is latched when the com-

mand is written.

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