6

AT25DF256

DS-25DF256–035D–2/2017

6.

Commands and Addressing

A valid instruction or operation must always be started by first asserting the CS pin. After the CS pin has been asserted,

the host controller must then clock out a valid 8-bit opcode on the SPI bus. Following the opcode, instruction dependent

information such as address and data bytes would then be clocked out by the host controller. All opcode, address, and

data bytes are transferred with the most-significant bit (MSB) first. An operation is ended by deasserting the CS pin.

Opcodes not supported by the AT25DF256 will be ignored by the device and no operation will be started. The device will

continue to ignore any data presented on the SI pin until the start of the next operation (CS pin being deasserted and

then reasserted). In addition, if the CS pin is deasserted before complete opcode and address information is sent to the

device, then no operation will be performed and the device will simply return to the idle state and wait for the next

operation.

Addressing of the device requires a total of three bytes of information to be sent, representing address bits A23-A0.

Since the upper address limit of the AT25DF256 memory array is 007FFFh, address bits A23-A15 are always ignored by

the device.

Table 6-1.

Command Listing

Command

Opcode

Clock

Frequency

Address

Bytes

Dummy

Bytes

Data

Bytes

Read Commands

Read Array

0Bh

0000 1011

Up to 104 MHz

3

1

1+

03h

0000 0011

Up to 33 MHz

3

0

1+

Dual Output Read

3Bh

0011 1011

Up to 50 MHz

3

1

1+

Program and Erase Commands

Page Erase

81h

1000 0001

Up to 104 MHz

3

0

0

Block Erase (4 Kbytes)

20h

0010 0000

Up to 104 MHz

3

0

0

Block Erase (32 Kbytes)

52h

0101 0010

Up to 104 MHz

3

0

0

D8h

1101 1000

Up to 104 MHz

3

0

0

Chip Erase

60h

0110 0000

Up to 104 MHz

0

0

0

C7h

1100 0111

Up to 104 MHz

0

0

0

Chip Erase (Legacy Command)

62h

0110 0010

Up to 104 MHz

0

0

0

Byte/Page Program (1 to 256 Bytes)

02h

0000 0010

Up to 104 MHz

3

0

1+

Protection Commands

Write Enable

06h

0000 0110

Up to 104 MHz

0

0

0

Write Disable

04h

0000 0100

Up to 104 MHz

0

0

0

Security Commands

Program OTP Security Register

9Bh

1001 1011

Up to 104 MHz

3

0

1+

Read OTP Security Register

77h

0111 0111

Up to 104 MHz

3

2

1+

Status Register Commands

Read Status Register

05h

0000 0101

Up to 104 MHz

0

0

1+

Write Status Register Byte 1

01h

0000 0001

Up to 104 MHz

0

0

1