Signal descriptions
M29W128GH, M29W128GL
2.7
Write Enable (W)
The Write Enable pin, W, controls the Bus Write operation of the memory’s command
interface.
2.8
VPP/Write Protect (VPP/WP)
The V /Write Protect pin provides two functions. The V
function allows the memory to
PP
PPH
use an external high voltage power supply to reduce the time required for program
operations. This is achieved by bypassing the unlock cycles.
The Write Protect function provides a hardware method of protecting the highest or lowest
block (see Section 1: Description). When V /Write Protect is Low, V , the highest or lowest
PP
IL
block is protected. Program and Erase operations on this block are ignored while V /Write
PP
Protect is Low.
When V /Write Protect is High, V , the memory reverts to the previous protection status
PP
IH
of the highest or lowest block. Program and Erase operations can now modify the data in
this block unless the block is protected using Block protection.
When V /Write Protect is raised to V
the memory automatically enters the Unlock
PP
PPH
Bypass mode (see Section 6.2.6).
When V /Write Protect is raised to V
, the execution time of the command is lower (see
PPH
PP
Table 17: Program, Erase times and Program, Erase endurance cycles).
When V /Write Protect returns to V or V normal operation resumes. During Unlock
PP
IH
IL
Bypass Program operations the memory draws I from the pin to supply the programming
PP
circuits. See the description of the Unlock Bypass command in the command interface
section. The transitions from V to V
and from V
to V must be slower than t
IH
PPH
PPH IH VHVPP
(see Figure 23: Accelerated program timing waveforms).
Never raise V /Write Protect to V from any mode except Read mode, otherwise the
PP
PPH
memory may be left in an indeterminate state. A 0.1 µF capacitor should be connected
between the VPP/Write Protect pin and the V ground pin to decouple the current surges
SS
from the power supply. The PCB track widths must be sufficient to carry the currents
required during Unlock Bypass Program (see I
, I
, I
, I
in Table 25: DC
PP1 PP2 PP3 PP4
characteristics).
The V /Write Protect pin may be left floating or unconnected because it features an
PP
internal pull-up.
Refer to Table 3 for a summary of V /WP functions.
PP
Table 3.
V
/WP functions
PP
VPP/WP
Function
Highest block protected on M29W128GH.
Lowest block protected on M29W128GL.
VIL
VIH
Highest and lowest block unprotected unless a software protection is
activated (see Section 4: Hardware protection).
Unlock bypass mode. It supplies the current needed to speed up
programming.
VPPH
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NUMONYX [ NUMONYX B.V ]
