AT25DF321A-MH-Y datasheet(8/52 Pages) ATMEL

8 / 52 page

3686D–DFLASH–12/09

Atmel AT25DF321A

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 clock signal once the initial starting address has been specified. The device incorporates an internal address

counter that automatically increments on every clock cycle.

Three opcodes (1Bh, 0Bh, and 03h) can be used for the Read Array command. The use of each opcode depends on the

maximum clock frequency that will be used to read data from the device. The 0Bh opcode can be used at any clock

frequency up to the maximum specified by f

CLK, and the 03h opcode can be used for lower frequency read operations up

to the maximum specified by f

RDLF. The 1Bh opcode allows the highest read performance possible and can be used at any

clock frequency up to the maximum specified by f

MAX; however, use of the 1Bh opcode at clock frequencies above fCLK

should be reserved to systems employing the Atmel

™ RapidS™ protocol.

To perform the Read Array operation, the CS pin must first be asserted and the appropriate opcode (1Bh, 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. Following the three address bytes,

additional dummy bytes may need to be clocked into the device depending on which opcode is used for the Read Array

operation. If the 1Bh opcode is used, then two dummy bytes must be clocked into the device after the three address

bytes. If the 0Bh opcode is used, then a single dummy byte must be clocked in after the address bytes.

After the three address bytes (and the dummy bytes or byte if using opcodes 1Bh or 0Bh) have been clocked in,

additional clock cycles will result in 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-impedance 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 – 1Bh Opcode

SCK

MSB

00011011

410 11

812

42 43

37 38

31 32

29 30

47 48

50 51

55 56

OPCODE

AAAA

AAA

MSB

XXXXXXX

MSB

DDDDDDD

ADDRESS BITS A23-A0

DON'T CARE

MSB

XXXXXXX

DON'T CARE

DATA BYTE 1

HIGH-IMPEDANCE

AT25DF321A-MH-Y Datenblatt(PDF) 8 Page - ATMEL Corporation

AT25DF321A-MH-Y Datenblatt(HTML) 8 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

Datenblatt Download

Link URL