AT25QL641 datasheet(49/77 Pages) DIALOG

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AT25QL641

DS-25QL641–130E–10/2018

Wrap Around in SPI mode

The ‘Word Read Quad I/O’ instruction can also be used to access a specific portion within a page by issuing a ‘Set

Burst with Wrap’ (77h) instruction prior to E7h. The ‘Set Burst with Wrap’ (77h) instruction can either enable or disable

the “Wrap Around” feature for the following E7h commands. When “Wrap Around” is enabled, the output data starts at

the initial address specified in the instruction, once it reaches the ending boundary of the 8/16/32/64-byte section,

the output wraps around to the beginning boundary automatically until CS is pulled high to terminate the instruction.

The Burst with Wrap feature allows applications that use cache to quickly fetch a critical address and then fill the cache

afterwards within a fixed length (8/16/32/64-byte) of data without issuing read instructions.

The “Set Burst with Wrap” instruction allows three “Wrap Bits”, W6-4 to be set. The W4 bit is used to enable or disable

the “Wrap Around” operation while W6-5 is used to specify the length of the wrap around section within a page.

7.32

Set Burst with Wrap (77h)

The ‘ Set Burst with Wrap’ (77h) instruction is used in conjunction with ‘Fast Read Quad I/O’ and ‘Word Read Quad

I/O’ instructions to access a fixed length of 8/16/32/64-byte section within a 256-byte page. Certain applications can

benefit from this feature and improve the overall system code execution performance. Before the device can accept the

‘Set Burst with Wrap’ instruction, the QE bit in the Status register bit must be set.

The ‘ Set Burst with Wrap’ instruction is initiated by driving the CS pin low and then shifting the instruction code

“77h” followed by 24 dummy bits and 8 “Wrap Bits”, W7-0. The instruction sequence is shown in ‘Set Burst with Wrap’

instruction sequence. Wrap bits W7 and W3-0 are not used.

Once W6-4 are set by a ‘Set Burst with Wrap’ instruction, all the following “Fast Read Quad I/O” and ‘Word Read Quad I/O’

instructions use the W6-4 setting to access the corresponding 8/16/32/64-byte section within any page.

To exit the “Wrap Around” function and return to normal read operation, another ‘Set Burst with Wrap’ instruction should be

issued to set W4 = 1. The default value of W4 upon power on is 1. In the case of a system reset while W4 = 0, it is

recommended that the controller issues a ‘Set Burst with Wrap’ instruction or Reset (99h) instruction to reset W4 = 1 prior to

any normal Read instructions since the AT25QL641 does not have an external hardware reset pin.

Table 7-6.

Encoding of the W6 - W4 Wrap Bits

W6, W5

W4 = 0

W4 = 1 (Default)

Wrap Around

Wrap Length

Wrap Around

Wrap Length

0 0

Yes

8-byte

N/A

0 1

Yes

16-byte

N/A

1 0

Yes

32-byte

N/A

1 1

Yes

64-byte

N/A

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