S75WS256NDFBAWMB datasheet(61/216 Pages) SPANSION

61 / 216 page

February 17, 2005 S75WS-N-00_A0

S75WS256Nxx Based MCPs

Advance

Information

9.6

Advanced Sector Protection Software Examples

Table 9.2 contains all possible combinations of the DYB, PPB, and PPB Lock Bit relating to the sta-

tus of the sector. In summary, if the PPB Lock Bit is locked (set to 0), no changes to the PPBs are

allowed. The PPB Lock Bit can only be unlocked (reset to 1) through a hardware reset or power

cycle. See also Figure 9.1 for an overview of the Advanced Sector Protection feature.

9.7

Hardware Data Protection Methods

The device offers two main types of data protection at the sector level via hardware control:

When WP# is at VIL, the four outermost sectors are locked (device specific).

When ACC is at VIL, all sectors are locked.

There are additional methods by which intended or accidental erasure of any sectors can be pre-

vented via hardware means. The following subsections describes these methods:

9.7.1

WP# Method

The Write Protect feature provides a hardware method of protecting the four outermost sectors.

This function is provided by the WP# pin and overrides the previously discussed Sector Protec-

tion/Unprotection method.

If the system asserts VIL on the WP# pin, the device disables program and erase functions in the

outermost boot sectors. The outermost boot sectors are the sectors containing both the lower and

upper set of sectors in a dual-boot-configured device.

If the system asserts VIH on the WP# pin, the device reverts to whether the boot sectors were

last set to be protected or unprotected. That is, sector protection or unprotection for these sectors

depends on whether they were last protected or unprotected.

Note that the WP# pin must not be left floating or unconnected as inconsistent behavior of the

device may result.

The WP# pin must be held stable during a command sequence execution

9.7.2

ACC Method

This method is similar to above, except it protects all sectors. Once ACC input is set to VIL, all

program and erase functions are disabled and hence all sectors are protected.

9.7.3

Low VCC Write Inhibit

When VCC is less than VLKO, the device does not accept any write cycles. This protects data during

VCC power-up and power-down.

Table 9.2

Unique Device PPB Lock Bit

0 = locked

1 = unlocked

Sector PPB

0 = protected

1 = unprotected

Sector DYB

0 = protected

1 = unprotected

Sector Protection Status

Any Sector

Protected through PPB

Any Sector

Protected through PPB

Any Sector

Unprotected

Any Sector

Protected through DYB

Any Sector

Protected through PPB

Any Sector

Protected through PPB

Any Sector

Protected through DYB

Any Sector

Unprotected

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