Signal descriptions
M29W640FT, M29W640FB
2.7
Write Enable (W)
The Write Enable, W, controls the Bus Write operation of the memory’s Command Interface.
2.8
V
PP
/Write Protect (V
PP
/WP)
The V
PP
/Write Protect pin provides two functions. The V
PP
function allows the memory to
use an external high voltage power supply to reduce the time required for Unlock Bypass
Program operations. The Write Protect function provides a hardware method of protecting
the two outermost boot blocks. The V
PP
/Write Protect pin must not be left floating or
unconnected.
When V
PP
/Write Protect is Low, V
IL
, the memory protects the two outermost boot blocks;
Program and Erase operations in this block are ignored while V
PP
/Write Protect is Low, even
when RP is at V
ID
.
When V
PP
/Write Protect is High, V
IH
, the memory reverts to the previous protection status
of the two outermost boot blocks. Program and Erase operations can now modify the data in
the two outermost boot blocks unless the block is protected using Block Protection.
Applying V
PPH
to the V
PP
/WP pin will temporarily unprotect any block previously protected
(including the two outermost parameter blocks) using a High Voltage Block Protection
technique (In-System or Programmer technique). See
for
details.
When V
PP
/Write Protect is raised to V
PP
the memory automatically enters the Unlock
Bypass mode. When V
PP
/Write Protect returns to V
IH
or V
IL
normal operation resumes.
During Unlock Bypass Program operations the memory draws I
PP
from the pin to supply the
programming circuits. See the description of the Unlock Bypass command in the Command
Interface section. The transitions from V
IH
to V
PP
and from V
PP
to V
IH
must be slower than
t
VHVPP
, see
Never raise V
PP
/Write Protect to V
PP
from any mode except Read mode, otherwise the
memory may be left in an indeterminate state.
A 0.1µF capacitor should be connected between the V
PP
/Write Protect pin and the V
SS
Ground pin to decouple the current surges from the power supply. The PCB track widths
must be sufficient to carry the currents required during Unlock Bypass Program, I
PP
.
Table 3.
V
PP
/WP
V
IL
V
IH
or V
ID
V
PPH
Hardware protection
RP
V
IH
V
ID
V
ID
V
IH
or V
ID
Function
2 outermost parameter blocks protected from Program/Erase operations
All blocks temporarily unprotected except the 2 outermost blocks
All blocks temporarily unprotected
All blocks temporarily unprotected
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NUMONYX [ NUMONYX B.V ]
