M29W320DT datasheet(13/56 Pages) STMICROELECTRONICS

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M29W320DT, M29W320DB

Signal descriptions

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2.7

Write Enable (W)

The Write Enable, W, controls the Bus Write operation of the memory’s Command Interface.

2.8

VPP/Write Protect (VPP/WP)

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 Unlock Bypass

Program operations. The Write Protect function provides a hardware method of protecting

the 16 Kbyte Boot Block. The VPP/Write Protect pin must not be left floating or unconnected.

When VPP/Write Protect is Low, VIL, the memory protects the 16 Kbyte Boot Block; Program

and Erase operations in this block are ignored while VPP/Write Protect is Low.

When VPP/Write Protect is High, VIH, the memory reverts to the previous protection status

of the 16 Kbyte boot block. Program and Erase operations can now modify the data in the 16

Kbyte Boot Block unless the block is protected using Block Protection.

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 13.

Never raise VPP/Write Protect to VPP 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 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.

2.9

Reset/Block Temporary Unprotect (RP)

The Reset/Block Temporary Unprotect pin can be used to apply a Hardware Reset to the

memory or to temporarily unprotect all Blocks that have been protected.

Note that if VPP/WP is at VIL, then the 16 KByte outermost boot block will remain protect

even if RP is at VID.

A Hardware Reset is achieved by holding Reset/Block Temporary Unprotect Low, VIL, for at

least tPLPX. After Reset/Block Temporary Unprotect goes High, VIH, the memory will be

ready for Bus Read and Bus Write operations after tPHEL or tRHEL, whichever occurs last.

See the Ready/Busy Output section, Table 15 and Figure 12, for more details.

Holding RP at VID will temporarily unprotect the protected Blocks in the memory. Program

and Erase operations on all blocks will be possible. The transition from VIH to VID must be

slower than tPHPHH.

M29W320DT Datasheet(PDF) 13 Page - STMicroelectronics