M29W640FT datasheet(13/72 Pages) STMICROELECTRONICS

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M29W640FT, M29W640FB

2 Signal descriptions

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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 two outermost boot blocks will remain protected 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 16: Reset/Block Temporary Unprotect AC Characteristics

and Figure 12: Reset/Block Temporary Unprotect AC Waveforms, 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.

2.10

Ready/Busy Output (RB)

The Ready/Busy pin is an open-drain output that can be used to identify when the device is

performing a Program or Erase operation. During Program or Erase operations Ready/Busy is

Low, VOL. Ready/Busy is high-impedance during Read mode, Auto Select mode and Erase

Suspend mode.

After a Hardware Reset, Bus Read and Bus Write operations cannot begin until Ready/Busy

becomes high-impedance. See Table 16: Reset/Block Temporary Unprotect AC Characteristics

and Figure 12: Reset/Block Temporary Unprotect AC Waveforms, for more details.

The use of an open-drain output allows the Ready/Busy pins from several memories to be

connected to a single pull-up resistor. A Low will then indicate that one, or more, of the

memories is busy.

2.11

Byte/Word Organization Select (BYTE)

The Byte/Word Organization Select pin is used to switch between the x8 and x16 Bus modes of

the memory. When Byte/Word Organization Select is Low, VIL, the memory is in x8 mode, when

it is High, VIH, the memory is in x16 mode.

2.12

VCC Supply Voltage (2.7V to 3.6V)

VCC provides the power supply for all operations (Read, Program and Erase).

The Command Interface is disabled when the VCC Supply Voltage is less than the Lockout

Voltage, VLKO. This prevents Bus Write operations from accidentally damaging the data during

power up, power down and power surges. If the Program/Erase Controller is programming or

erasing during this time then the operation aborts and the memory contents being altered will

be invalid.

A 0.1

µF capacitor should be connected between the V

CC Supply Voltage 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 Program and Erase operations, ICC3.

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