s29cd-j Meet Spansion Inc., s29cd-j Datasheet - Page 42

• Manufacturer Part Number: s29cd-j
• Description: 32/16 Megabit Cmos 2.6 Volt Or 3.3 Volt-only Simultaneous Read/write, Dual Boot, Burst Mode Flash Memory With Versatilei/o?
• Manufacturer: Meet Spansion Inc.

9.1
9.2
42
Advanced Sector Protection Overview
Persistent Protection Bits
As shipped from the factory, all devices default to the persistent mode when power is applied, and all sector
groups are unprotected. The device programmer or host system must then choose which sector group
protection method to use. Programming (setting to “0”) any one of the following two one-time programmable,
non-volatile bits locks the device permanently in that mode:
After selecting a sector group protection method, each sector group can operate in any of the following three
states:
These states are controlled by the bit types described between page 42 and page 46.
Notes
The Persistent Protection Bits are unique and nonvolatile. A single Persistent Protection Bit is assigned to a
maximum for four sectors (see the sector address tables for specific sector protection groupings). All eight-
Kbyte boot-block sectors have individual sector Persistent Protection Bits (PPBs) for greater flexibility.
Notes
Persistent Protection Mode Lock Bit
Password Protection Mode Lock Bit
1. Persistently Locked. A sector group is protected and cannot be changed.
2. Dynamically locked. The selected sector groups are protected and can be altered via software
3. Unlocked. The sector groups are unprotected and can be erased and/or programmed.
1. If the password mode is chosen, the password must be programmed before setting the
2. If both lock bits are selected to be programmed (to zeros) at the same time, the operation aborts.
3. Once the Password Mode Lock Bit is programmed, the Persistent Mode Lock Bit is permanently
4. It is important that the mode is explicitly selected when the device is first programmed, rather than
5. If the user attempts to program or erase a protected sector, the device ignores the command and
6. For the command sequence required for programming the lock register bits, refer to
1. Each PPB is individually programmed and all are erased in parallel. There are no means for
2. If a PPB requires erasure, all of the sector PPBs must first be programmed prior to PPB erasing. It
3. If the PPB Lock Bit is set, the PPB Program or erase command does not execute and times-out
commands.
corresponding lock register bit. The user must be sure that the password is correct when the
Password Mode Locking Bit is set, as there is no means to verify the password afterwards.
disabled, and no changes to the protection scheme are allowed. Similarly, if the Persistent Mode
Lock Bit is programmed, the Password Mode is permanently disabled.
relying on the default mode alone. This is so that it is impossible for a system program or virus to
later set the Password Mode Locking Bit, which would cause an unexpected shift from the default
Persistent Sector Protection Mode into the Password Protection Mode.
returns to read mode. A program command to a protected sector enables status polling for
approximately 1 µs before the device returns to read mode without modifying the contents of the
protected sector. An erase command to a protected sector enables status polling for approximately
50 µs, after which the device returns to read mode without having erased the protected sector.
Command Definitions on page
individually erasing a specific PPB and no specific sector address is required for this operation.
is the responsibility of the user to perform the preprogramming operation. Otherwise, an already
erased sector PPB has the potential of being over-erased. There is no hardware mechanism to
prevent sector PPB over-erasure.
without programming or erasing the PPB.
S29CD-J & S29CL-J Flash Family
D a t a
72.
S h e e t
( P r e l i m i n a r y )
S29CD-J_CL-J_00_B2 March 7, 2007
Section 20.1,