7

3633C–DFLASH–08/06

AT26DF321 [Preliminary]

7.

Read Commands

7.1

Read Array

The Read Array command can be used to sequentially read a continuous stream of data from

the device by simply providing the SCK signal once the initial starting address has been speci-

fied. The device incorporates an internal address counter that automatically increments on every

clock cycle.

Two opcodes, 0Bh and 03h, can be used for the Read Array command. The use of each opcode

depends on the maximum SCK frequency that will be used to read data from the device. The

0Bh opcode can be used at any SCK frequency up to the maximum specified by f

opcode can be used for lower frequency read operations up to the maximum specified by f

To perform the Read Array operation, the CS pin must first be asserted and the appropriate

opcode (0Bh or 03h) 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. If the 0Bh opcode is used, then one don’t care byte must also be

clocked in after the three address bytes.

After the three address bytes (and the one don’t care byte if using opcode 0Bh) have been

clocked in, additional clock cycles will result in serial data being output on the SO pin. The data

is always output with the MSB of a byte first. 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 pin into a high-imped-

ance state. The CS pin can be deasserted at any time and does not require that a full byte of

data be read.

Figure 7-1.

Read Array – 0Bh Opcode

Figure 7-2.

Read Array – 03h Opcode

SCK

CS

SI

SO

MSB

MSB

23

1

0

00001011

67

5

410 11

9

812

39

42 43

41

40

37 38

33

36

35

34

31 32

29 30

44

47 48

46

45

OPCODE

AAAA

AAA

A

A

MSB

XXXXXXX

X

MSB

MSB

DDDDDDD

D

D

D

ADDRESS BITS A23-A0

DON'T CARE

DATA BYTE 1

HIGH-IMPEDANCE

SCK

CS

SI

SO

MSB

MSB

23

1

0

00000011

67

5

410 11

9

812

37 38

33

36

35

34

31 32

29 30

39 40

OPCODE

AAAA

AAA

A

A

MSB

MSB

DDDDDDD

D

D

D

ADDRESS BITS A23-A0

DATA BYTE 1

HIGH-IMPEDANCE