M28W640HCT datasheet(16/72 Pages) NUMONYX

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Command interface

M28W640HCT, M28W640HCB

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Command interface

All bus write operations to the memory are interpreted by the command interface.

Commands consist of one or more sequential bus write operations. An internal

Program/Erase controller handles all timings and verifies the correct execution of the

Program and Erase commands. The Program/Erase controller provides a Status Register

whose output may be read at any time to monitor the progress of the operation, or the

Program/Erase states. See Table 3: Command codes, for a summary of the commands and

see Appendix D, Table 31: Write state machine current/next, for a summary of the command

interface.

The command interface is reset to Read mode when power is first applied, when exiting

from reset or whenever VDD is lower than VLKO. Command sequences must be followed

exactly. Any invalid combination of commands will reset the device to Read mode. Refer to

Table 4: Commands, in conjunction with the text descriptions below.

4.1

Read Memory Array command

The Read command returns the memory to its Read mode. One Bus Write cycle is required

to issue the Read Memory Array command and return the memory to Read mode.

Subsequent read operations will read the addressed location and output the data. When a

device Reset occurs, the memory defaults to Read mode.

4.2

Read Status Register command

The Status Register indicates when a program or erase operation is complete and the

success or failure of the operation itself. Issue a Read Status Register command to read the

Status Register’s contents. Subsequent bus read operations read the Status Register at any

address, until another command is issued. See Table 11: Status Register bits, for details on

the definitions of the bits.

The Read Status Register command may be issued at any time, even during a

program/erase operation. Any read attempt during a program/erase operation will

automatically output the content of the Status Register.

4.3

Read Electronic Signature command

The Read Electronic Signature command reads the manufacturer and device codes and the

Block Locking Status, or the Protection Register.

The Read Electronic Signature command consists of one write cycle, a subsequent read will

output the manufacturer code, the device code, the Block Lock and Lock-Down Status, or

the Protection and Lock Register. See Tables 5, 6 and 7 for the valid address.

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