S29CD016G SPANSION, S29CD016G Datasheet - Page 55

• Manufacturer Part Number: S29CD016G
• Description: 16 Megabit (512 K x 32-Bit) CMOS 2.5 Volt-only Burst Mode / Dual Boot / Simultaneous Read/Write Flash Memory
• Manufacturer: SPANSION

November 5, 2004 S29CD016_00_A4
DYB Write Command
Password Unlock Command
PPB Program 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.
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 accessible
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 at-
tempt 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 com-
mand 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. A0 is used to determine whether the 32 bit data
quantity is used to match the upper 32 bits or lower 32 bits. Writing the Password
Unlock command is address order specific. In other words, for the x32 data bus
configuration, the lower 32 bits of the password are written first and then the
upper 32 bits of the password are written. Writing out of sequence results in the
Password Unlock not returning a match with the password and the PPB Lock Bit
remains set.
cating that the device is busy. Also, reading the small bank (25% bank) results
in the DQ6 pin toggling, indicating that the Password Unlock function is in
progress. Reading the large bank (75% bank) returns actual array data. Approx-
imately 1uSec 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 command is issued again, only this time with
the next part of the password. The second Password Unlock command is the final
command before the PPB Lock Bit is cleared (assuming a valid password). 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 num-
ber of Password Unlock commands (2 for x32 bus), the order, and when to read
the PPB Lock bit to confirm successful password unlock
The Password Unlock command is permitted if the SecSi sector is enabled.
The PPB Program command is used to program, or set, a given PPB. Each PPB is
individually programmed (but is bulk erased with the other PPBs). The specific
sector address (A18–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.
Once the Password Unlock command is entered, the RY/BY# pin goes LOW indi-
A d v a n c e
I n f o r m a t i o n
S29CD016G
55