AT25DF256 datasheet(21/47 Pages) RENESAS

21 / 47 page

DS-AT25DF256-035 Rev.G

Page 21

2024-01-08

AT25DF256 Datasheet

uneven byte boundaries, or because the user-programmable portion of the OTP Security Register was previously

programmed.

While the device is programming the OTP Security Register, the Status Register can be read and indicates that

the device is busy. For faster throughput, it is recommended that the Status Register be polled rather than waiting

the tOTPP time to determine if the data bytes have finished programming. At some point before the OTP Security

If the device is powered-down during the OTP Security Register program cycle, then the contents of the 64-byte

user programmable portion of the OTP Security Register cannot be guaranteed and cannot be programmed

again.

The Program OTP Security Register command uses the internal 256-buffer for processing. Thus, the contents of

the buffer are altered from the previous state when this command is issued.

Figure 16. Program OTP Security Register

10.2 Read OTP Security Register

The OTP Security Register can be sequentially read in a similar fashion to the Read Array operation up to the

maximum clock frequency specified by fCLK. To read the OTP Security Register, the CS pin must first be asserted

and the opcode of 77h 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 OTP Security

output.

After the three address bytes and the dummy bytes have been clocked in, additional clock cycles result in OTP

Security Register data being output on the SO pin. When the last byte (00007Fh) of the OTP Security Register

has been read, the device continues reading at the beginning of the register (000000h). No delays are incurred

when wrapping around from the end of the register to the beginning of the register.

Deasserting the CS pin stops the read operation and puts 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 17. Read OTP Security Register

SCK

MSB

10011011

839

37 38

31 32

29 30

OPCODE

HIGH-IMPEDANCE

AAA

MSB

DDDDDDD

ADDRESS BITS A23-A0

DATA IN BYTE 1

MSB

DDDDDDD

DATA IN BYTE n

SCK

MSB

01110111

410 11

812

31 32

29 30

OPCODE

AAAA

AAA

MSB

DDDDDDD

ADDRESS BITS A23-A0

MSB

XXXXX

DON'T CARE

DATA BYTE 1

HIGH-IMPEDANCE

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