M29W640DB datasheet(13/49 Pages) STMICROELECTRONICS

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M29W640DT, M29W640DB

Quadruple Byte Program command is available for

x8 operations, while the Double Word Program

command is available for x16 operations.

Quadruple Byte Program Command. The Qua-

druple Byte Program command is used to write a

page of four adjacent Bytes in parallel. The four

bytes must differ only for addresses A0, DQ15A-1.

Five bus write cycles are necessary to issue the

Quadruple Byte Program command.

■

The first bus cycle sets up the Quadruple Byte

Program Command.

■

The second bus cycle latches the Address and

the Data of the first byte to be written.

■

The third bus cycle latches the Address and

the Data of the second byte to be written.

■

The fourth bus cycle latches the Address and

the Data of the third byte to be written.

■

The fifth bus cycle latches the Address and the

Data of the fourth byte to be written and starts

the Program/Erase Controller.

Double Word Program Command.

The Double Word Program command is used to

write a page of two adjacent words in parallel. The

two words must differ only for the address A0. Pro-

gramming should not be attempted when VPP is

not at VPPH.

Three bus write cycles are necessary to issue the

Double Word Program command.

■

The first bus cycle sets up the Double Word

Program 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 and

starts the Program/Erase Controller.

After the program operation has completed the

memory will return to the Read mode, unless an

error has occurred. When an error occurs Bus

Read operations will continue to output the Status

to reset the error condition and return to Read

mode.

Note that the Fast Program commands cannot

change a bit set at ’0’ back to ’1’. One of the Erase

Commands must be used to set all the bits in a

block or in the whole memory from ’0’ to ’1’.

Typical Program

times are given in Table

6., Program, Erase Times and Program, Erase

Endurance Cycles.

Unlock Bypass Command.

The Unlock Bypass command is used in conjunc-

tion 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 By-

pass command.

Once the Unlock Bypass command has been is-

sued the memory will only accept the Unlock By-

pass 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 By-

pass mode and the Unlock Bypass Program com-

mand can be issued immediately.

Unlock Bypass Program Command.

The Unlock Bypass command is used in conjunc-

tion 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 By-

pass command.

Once the Unlock Bypass command has been is-

sued the memory will only accept the Unlock By-

pass Program command and the Unlock Bypass

Reset command. The memory can be read as if in

Read mode.

The memory offers accelerated program opera-

tions through the VPP/Write Protect pin. When the

system asserts VPP on the VPP/Write Protect pin,

the memory automatically enters the Unlock By-

pass mode. The system may then write the two-

cycle Unlock Bypass program command se-

quence. 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.

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.

Chip Erase Command.

The Chip Erase command can be used to erase

the entire chip. Six Bus Write operations are re-

quired to issue the Chip Erase Command and start

the Program/Erase Controller.

If any blocks are protected then these are ignored

and all the other blocks are erased. If all of the

blocks are protected the Chip Erase operation ap-

pears to start but will terminate within about 100µs,

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