AT25DF256 datasheet(13/47 Pages) RENESAS

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DS-AT25DF256-035 Rev.G

Page 13

2024-01-08

AT25DF256 Datasheet

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 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 then the opcode

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 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 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 seven of the first data byte is output on the SO pin,

while bit six of the same data byte is output on the SIO pin. During the next clock cycle, bits five and four of the

first data byte are 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 (007FFFh) of the memory array has been read, the

device continues reading from 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 and SI 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.

Figure 9. Dual-Output Read Array

AT25DF256 Datasheet(PDF) 13 Page - Renesas Technology Corp