AT25D16-MH-B データシートの表示（PDF） - Atmel Corporation

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AT25D16-MH-B

16-Megabit 2.7-volt Minimum SPI Serial Flash Memory

Atmel Corporation 

AT25DF161 [Preliminary]

Figure 8-8. Program/Erase Resume

CS

SCK

SI

SO

01234567

OPCODE

11010000

MSB

HIGH-IMPEDANCE

9. Protection Commands and Features

9.1 Write Enable

The Write Enable command is used to set the Write Enable Latch (WEL) bit in the Status Regis-

ter to a logical “1” state. The WEL bit must be set before a Byte/Page Program, erase, Protect

Sector, Unprotect Sector, Sector Lockdown, Freeze Sector Lockdown State, Program OTP

Security Register, or Write Status Register command can be executed. This makes the issuance

of these commands a two step process, thereby reducing the chances of a command being

accidentally or erroneously executed. If the WEL bit in the Status Register is not set prior to the

issuance of one of these commands, then the command will not be executed.

To issue the Write Enable command, the CS pin must first be asserted and the opcode of 06h

must be clocked into the device. No address bytes need to be clocked into the device, and any

data clocked in after the opcode will be ignored. When the CS pin is deasserted, the WEL bit in

the Status Register will be set to a logical “1”. The complete opcode must be clocked into the

device before the CS pin is deasserted, and the CS pin must be deasserted on an even byte

boundary (multiples of eight bits); otherwise, the device will abort the operation and the state of

the WEL bit will not change.

Figure 9-1. Write Enable

CS

SCK

SI

SO

01234567

OPCODE

00000110

MSB

HIGH-IMPEDANCE

21

3687C–DFLASH–7/09

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