M29W640FT datasheet(25/72 Pages) STMICROELECTRONICS

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M29W640FT, M29W640FB

4 Command Interface

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4.2.5

Quadruple Word Program command

This is used to write a page of four adjacent Words (or 8 adjacent Bytes), in x16 mode,

simultaneously. The addresses of the four Words must differ only in A1 and A0.

Five bus write cycles are necessary to issue the command:

The first bus cycle sets up the command.

The second bus cycle latches the Address and the Data of the first Word to be written.

The third bus cycle latches the Address and the Data of the second Word to be written.

The fourth bus cycle latches the Address and the Data of the third Word to be written.

The fifth bus cycle latches the Address and the Data of the fourth Word to be written and

starts the Program/Erase Controller.

4.2.6

Unlock Bypass command

The Unlock Bypass command is used in conjunction with the Unlock Bypass Program

command to program the memory faster than with the standard program commands. When the

cycle time to the device is long, considerable time saving can be made by using these

commands. Three Bus Write operations are required to issue the Unlock Bypass command.

Once the Unlock Bypass command has been issued the memory will only accept the Unlock

Bypass Program command and the Unlock Bypass Reset command. The memory can be read

as if in Read mode.

When VPP is applied to the VPP/Write Protect pin the memory automatically enters the Unlock

Bypass mode and the Unlock Bypass Program command can be issued immediately.

4.2.7

Unlock Bypass Program command

The Unlock Bypass command is used in conjunction with the Unlock Bypass Program

command to program the memory. When the cycle time to the device is long, considerable time

saving can be made by using these commands. Three Bus Write operations are required to

issue the Unlock Bypass command.

Once the Unlock Bypass command has been issued the memory will only accept the Unlock

Bypass Program command and the Unlock Bypass Reset command. The memory can be read

as if in Read mode.

The memory offers accelerated program operations through the VPP/Write Protect pin. When

the system asserts VPP on the VPP/Write Protect pin, the memory automatically enters the

Unlock Bypass mode. The system may then write the two-cycle Unlock Bypass program

command sequence. The memory uses the higher voltage on the VPP/Write Protect pin, to

accelerate the Unlock Bypass Program operation.

Never raise VPP/Write Protect to VPP from any mode except Read mode, otherwise the

memory may be left in an indeterminate state.

4.2.8

Unlock Bypass Reset command

The Unlock Bypass Reset command can be used to return to Read/Reset mode from Unlock

Bypass Mode. Two Bus Write operations are required to issue the Unlock Bypass Reset

command. Read/Reset command does not exit from Unlock Bypass Mode.

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