9

3686I–DFLASH–02/2019

AT25DF321A

Figure 7-2.

Read Array – 0Bh Opcode

Figure 7-3.

Read Array – 03h Opcode

7.2

Dual-Output Read Array

The Dual-Output Read Array command is similar to the standard Read Array command and can be used to sequentially read a

continuous stream of data from the device by simply providing the clock signal once the initial starting address has been

specified. Unlike the standard Read Array command, however, the Dual-Output Read Array command allows two bits of data

to be clocked out of the device on every clock cycle rather than just one.

The Dual-Output Read Array command can be used at any clock frequency up to the maximum specified by fRDDO. To

perform the Dual-Output Read Array operation, the CS pin must first be asserted and the opcode of 3Bh must be clocked into

the device. After the opcode has been clocked in, the three address bytes must be clocked in to specify the starting address

location of the first byte to read within the memory array. Following the three address bytes, a single dummy byte must also be

clocked into the device.

After the three address bytes and the dummy byte have been clocked in, additional clock cycles will result in data being output

on both the SO and SIO pins. The data is always output with the MSB of a byte first, and the MSB is always output on the SO

pin. During the first clock cycle, bit 7 of the first data byte will be output on the SO pin while bit 6 of the same data byte will

be output on the SIO pin. During the next clock cycle, bits 5 and 4 of the first data byte will be output on the SO and SIO pins,

respectively. The sequence continues with each byte of data being output after every four clock cycles. When the last byte

(3FFFFFh) of the memory array has been read, the device will continue reading back at the beginning of the array (000000h).

No delays will be incurred when wrapping around from the end of the array to the beginning of the array.

Deasserting the CS pin will terminate the read operation and put the SO and SIO pins into a high-impedance state. The CS pin

can be deasserted at any time and does not require that a full byte of data be read.

SCK

CS

SI

SO

MSB

MSB

2

3

1

0

0

0

0

0

1

0

1

1

6

7

5

4

10 11

9

8

12

39

42 43

41

40

37 38

33

36

35

34

31 32

29 30

44

47 48

46

45

OPCODE

A

A

A

A

A

A

A

A

A

MSB

X

X

X

X

X

X

X

X

MSB

MSB

D

D

D

D

D

D

D

D

D

D

ADDRESS BITS A23-A0

DON'T CARE

DATA BYTE 1

HIGH-IMPEDANCE

SCK

CS

SI

SO

MSB

MSB

2

3

1

0

0

0

0

0

0

0

1

1

6

7

5

4

10 11

9

8

12

37 38

33

36

35

34

31 32

29 30

39 40

OPCODE

A

A

A

A

A

A

A

A

A

MSB

MSB

D

D

D

D

D

D

D

D

D

D

ADDRESS BITS A23-A0

DATA BYTE 1

HIGH-IMPEDANCE