AT25DF256 datasheet(12/47 Pages) RENESAS

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DS-AT25DF256-035 Rev.G

Page 12

2024-01-08

AT25DF256 Datasheet

Read Commands

7.1

Read Array

The Read Array command sequentially reads a continuous stream of data from the device by providing the clock

signal once the initial starting address is specified. The device incorporates an internal address counter that

automatically increments 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 clock frequency used to read data from the device. The 0Bh opcode can be used at any clock

frequency up to the maximum specified by fCLK, and the 03h opcode can be used for lower frequency read

operations up to the maximum specified by fRDLF.

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. Following the three

address bytes, an additional dummy byte must be clocked into the device if the 0Bh opcode is used for the Read

Array operation.

After the three address bytes (and the dummy byte if using opcode 0Bh) have been clocked in, additional clock

cycles 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 (007FFFh) of the memory array has been read, the device continues reading at the beginning of the

array (000000h). No delays are incurred when wrapping around from the end of the array to the beginning of the

array.

Deasserting the CS pin stops the read operation and puts the SO pin into high-impedance state. The CS pin can

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

Figure 7. Read Array - 03h Opcode

Figure 8. Read Array - 0Bh Opcode

SCK

MSB

00000011

410 11

812

37 38

31 32

29 30

39 40

OPCODE

AAAA

AAA

MSB

DDDDDDD

ADDRESS BITS A23-A0

DATA BYTE 1

HIGH-IMPEDANCE

SCK

MSB

00001011

410 11

812

42 43

37 38

31 32

29 30

47 48

OPCODE

AAAA

AAA

MSB

XXXXXXX

MSB

DDDDDDD

ADDRESS BITS A23-A0

DON'T CARE

DATA BYTE 1

HIGH-IMPEDANCE

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