M29W128FH, M29W128FL
Signal descriptions
2.7
Write Enable (W)
The Write Enable pin, W, controls the Bus Write operation of the memory’s Command
Interface.
2.8
V Write Protect (V /WP)
PP/
PP
The VPP/Write Protect pin provides two functions. The VPP function allows the memory to
use an external high voltage power supply to reduce the time required for Program
operations. This is achieved by bypassing the unlock cycles and/or using the multiple Word
(2 or 4 at-a-time) or multiple Byte Program (2, 4 or 8 at-a-time) commands.
The Write Protect function provides a hardware method of protecting the highest or lowest
block. When VPP/Write Protect is Low, VIL, the highest or lowest block is protected; Program
and Erase operations on this block are ignored while VPP/Write Protect is Low, even when
RP is at VID.
When VPP/Write Protect is High, VIH, the memory reverts to the previous protection status
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.
Applying VPPH to the VPP/WP pin will temporarily unprotect any block previously protected
(including the highest or lowest block) using a High Voltage Block Protection technique (In-
System or Programmer technique). See Table 8: Hardware Protection for details.
When VPP/Write Protect is raised to VPP the memory automatically enters the Unlock
Bypass mode. When VPP/Write Protect returns to VIH or VIL normal operation resumes.
During Unlock Bypass Program operations the memory draws IPP from the pin to supply the
programming circuits. See the description of the Unlock Bypass command in the Command
Interface section. The transitions from VIH to VPP and from VPP to VIH must be slower than
tVHVPP (see Figure 15: Accelerated Program Timing waveforms).
Never raise VPP/Write Protect to VPP from any mode except Read mode, otherwise the
memory may be left in an indeterminate state.
The VPP/Write Protect pin must not be left floating or unconnected or the device may
become unreliable. A 0.1µF capacitor should be connected between the VPP/Write Protect
pin and the VSS 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,
IPP.
13/78
NUMONYX [ NUMONYX B.V ]
