M29W320DT datasheet(14/56 Pages) STMICROELECTRONICS

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Signal descriptions

M29W320DT, M29W320DB

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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.

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

even if RP is at VID.

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

becomes high-impedance. See Table 15 and Figure 12.

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

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 0.1µF capacitor should be connected between the VCC 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.

2.13

VSS Ground

VSS is the reference for all voltage measurements.

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