SST26VF016BEUI datasheet(7/78 Pages) MICROCHIP

7 / 78 page

 2019 Microchip Technology Inc.

DS20006153A-page 7

SST26VF016BEUI

lock, and the least significant bit is for write-lock. Read-

locking the parameter blocks provides additional secu-

rity for sensitive data after retrieval (e.g., after initial

boot). If a block is read-locked all reads to the block

return data 00H.

The Write Block-Protection Register command is a

two-cycle command which requires that Write-Enable

(WREN) is executed prior to the Write Block-Protection

Unlock command clears all write protection bits in the

Block-Protection register.

4.1.2

WRITE-PROTECTION LOCK-DOWN

(VOLATILE)

To prevent changes to the Block-Protection register,

use the Lock-Down Block-Protection Register (LBPR)

command to enable Write-Protection Lock-Down.

Once Write-Protection Lock-Down is enabled, the

Block-Protection register can not be changed. To avoid

inadvertent lock down, the WREN command must be

executed prior to the LBPR command.

To reset Write-Protection Lock-Down, performing a power

cycle on the device is required. The Write-Protection Lock-

Down status may be read from the Status register.

4.1.3

WRITE-LOCK LOCK-DOWN (NON-

VOLATILE)

The non-Volatile Write-Lock Lock-Down register is an

alternate register that permanently prevents changes

to the block-protect bits. The non-Volatile Write-Lock

Lock-Down register (nVWLDR) is 40 bits wide per

device: one bit each for the eight 8-KByte parameter

blocks, and one bit each for the remaining 32 KByte

and 64 KByte overlay blocks. See Table 5-6 for address

range protected per register bit.

Writing ‘1’ to any or all of the nVWLDR bits disables the

change mechanism for the corresponding Write-Lock

bit in the BPR, and permanently sets this bit to a ‘1’

(protected) state. After this change, both bits will be set

to ‘1’, regardless of the data entered in subsequent

writes to either the nVWLDR or the BPR. Subsequent

writes to the nVWLDR can only alter available locations

that have not been previously written to a ‘1’. This

method provides write-protection for the corresponding

memory-array block by protecting it from future pro-

gram or erase operations.

Writing a ‘0’ in any location in the nVWLDR has no

effect on either the nVWLDR or the corresponding

Write-Lock bit in the BPR.

Note that if the Block-Protection register had been pre-

viously locked down, see “Write-Protection Lock-Down

(Volatile)”, the device must be power cycled before

using the nVWLDR. If the Block-Protection register is

locked down and the Write nVWLDR command is

accessed, the command will be ignored.

4.2

Hardware Write Protection

The hardware Write Protection pin (WP#) is used in con-

junction with the WPEN and IOC bits in the configuration

tion and Configuration registers. The WP# pin function

only works in SPI single-bit and dual-bit read mode when

the IOC bit in the configuration register is set to ‘0’.

The WP# pin function is disabled when the WPEN bit

in the configuration register is ‘0’. This allows installa-

tion of SST26VF016BEUI in a system with a grounded

WP# pin while still enabling Write to the Block-Protec-

tion register. The Lock-Down function of the Block-Pro-

tection Register supersedes the WP# pin, see Table 4-

1 for Write Protection Lock-Down states.

The factory default setting at power-up of the WPEN bit

is ‘0’, disabling the Write Protect function of the WP#

after power-up. WPEN is a non-volatile bit; once the bit

is set to ‘1’, the Write Protect function of the WP# pin

continues to be enabled after power-up. The WP# pin

only protects the Block-Protection Register and Config-

uration Register from changes. Therefore, if the WP#

pin is set to low before or after a Program or Erase

command, or while an internal Write is in progress, it

will have no effect on the Write command.

The IOC bit takes priority over the WPEN bit in the con-

figuration register. When the IOC bit is ‘1’, the function

of the WP# pin is disabled and the WPEN bit serves no

function. When the IOC bit is ‘0’ and WPEN is ‘1’, set-

ting the WP# pin active low prohibits Write operations

to the Block Protection Register.

TABLE 4-1:

WRITE PROTECTION LOCK-DOWN STATES

WP#

IOC

WPEN

WPLD

Execute WBPR Instruction

Configuration Register

Not Allowed

Protected

Not Allowed

Writable

Not Allowed

Protected

L01

Allowed

Writable

Not Allowed

Writable

Allowed

Writable

Not Allowed

Writable

Allowed

Writable

1. Default at power-up Register settings

2. Factory default setting is ‘0’. This is a non-volatile bit; default at power-up is the value set prior to power-down.

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