s29ns01gs Meet Spansion Inc., s29ns01gs Datasheet - Page 50

• Manufacturer Part Number: s29ns01gs
• Description: S29ns01gs 1024 Megabit 128 Megabyte 16-bit Data Width, Burst Access, Simultaneous Read/write, 1.8 Volt-only Flash Memory In 65 Nm Mirrorbit Technology
• Manufacturer: Meet Spansion Inc.

8.3
50
8.2.3
Sector Lock Range (SLR) Command
POR Unlocked Mode
Following Power On Reset (POR) a special mode is made active that removes protection from all Flash
memory array sectors that are not protected by ACC being at V
the Secure Silicon Region. This mode is intended to simplify programming of multiple sectors during system
production in a factory environment. This mode is made inactive, leaving all sectors protected by default,
when either the Sector Lock Range or Sector Lock/Unlock command is issued. Generally these commands
are issued by boot code so that the POR Unlock mode is inactive during normal system operation, thus
leaving all sectors protected by default.
This command allows a range of sectors to be protected from program or erase (locked) until a hardware
reset or power is removed from the device. This command causes the Sector Lock/Unlock command to be
ignored for the range of sectors.
This command is generally used by trusted boot code. After power on reset, boot code has the option to
check for any need to update sectors before locking them for the remainder of power on time. Once boot code
is satisfied with the content of sectors to be protected the Sector Lock Range command is used to lock
selected sectors against any program or erase during normal system operation. This adds an extra layer of
protection for critical data that must be protected against accidental or malicious corruption. Yet, maintains
flexibility for trusted boot code to perform occasional updates of the data. It is important to issue the Sector
Lock Range command even if no sectors are to be protected so that sectors that should remain available for
update cannot be later locked by accidental or malicious code behavior.
Two cycles are first written: addresses are CAP1 and CAP2 with data 60h. During the third cycle, the SLR
Low Address (SLA) and load sector address command (61h) is written. This cycle sets the lower sector
address of the range. During the fourth cycle, a sector address (SA) and load sector address command (61h)
is written. This cycle sets the upper sector address of the range. The addresses reference a large sector
address range (128 KBytes). The sectors selected by the lower and upper address, as well as all sectors
between these sectors, are protected from program and erase until a hardware reset or power is removed. If
the lower and upper sector addresses are for the same sector then only that one sector is locked. If the first
sector address cycle contains an address which is higher than the second sector address cycle, then the
command sequence will be invalid and ignored.
If the address range includes an area where four small sectors are located all four sectors are protected. If the
small sector area is not selected then the least significant 4 bits of the SLA control the lock status of the four
small sectors. System address a1 (Flash A0) controls the highest small sector for top boot. System address
a2 (Flash A1) controls the next higher or lower sector respectively and so on.
When one of the address inputs is a One (at V
Zero the related small sector is unprotected. These address inputs are ignored in a device with uniform large
sectors.
Flash address input A6 (system byte address bit a7) during both address cycles must be Zero (A6 = V
both of the large sector addresses to be accepted as valid. If A6 is One during both address cycles the SLR
command is valid but, neither large sector address is valid so, no large sector is locked by the SLR command.
If A6 is not Zero or One in both address cycles the command is invalid and ignored.
In either of the valid command cases - with A6 at Zero or One on both write cycles - the Flash addresses A3
to A0 are used to set the protection on the 4 small sectors as described earlier.
A valid Sector Lock Range command sequence is accepted only once after a Hardware Reset or initial power
up. Additional Sector Lock Range commands will be ignored.
When the device is first powered up, all sectors are unlocked. Writing the SLR command will make the POR
Unlock mode inactive which causes all sectors to be protected by default since no sector is explicitly
unlocked.
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