M29W640GH, M29W640GL, M29W640GT, M29W640GB
Signal descriptions
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 performs hardware protection:
●
●
It protects the first and last block on M29W640GH and M29W640GL devices.
It protects the first two and the last two boot blocks on M29W640GT and M29W640GB
devices.
The V
PP
/Write Protect pin may be left floating or unconnected (see
When V
PP
/Write Protect is Low, V
IL
, the two outermost (M29W640GH and M29W640GL) or
four outermost blocks (M29W640GT and M29W640GB) are protected. 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 outermost blocks. Program and Erase operations can now modify the data in the
outermost blocks unless the block is protected using Block Protection.
Applying 12V to the V
PP
/WP pin will temporarily unprotect any block previously protected
(including the outermost 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 6.
V
PP
/WP
Hardware Protection
RP
M29W640GT and
M29W640GB
V
IH
M29W640GH and
M29W640GL
M29W640GT and
M29W640GB
V
ID
M29W640GH and
M29W640GL
Function
4 outermost parameter blocks protected from
Program/Erase operations
2 outermost blocks protected from Program/Erase
operations
All blocks temporarily unprotected except the 4 outermost
blocks
All blocks temporarily unprotected except the 2 outermost
blocks
V
IL
15/90
NUMONYX [ NUMONYX B.V ]
