GD25Q21 datasheet(24/49 Pages) ELM

24 / 49 page

Rev.1.1

49 -

http://www.elm-tech.com

GD25Q21BxIGx Uniform Sector Dual and Quad Serial Flash

Figure 17. Quad I/O Word Fast Read Sequence Diagram (M7-0 = AXH)

0 1 2 3 4 5 6 7

CS#

SCLK

8 9 10 11 12 13 14 15

SI(IO0)

SO(IO1)

WP#(IO2)

HOLD#(IO3)

4 0 4 0

5 1 5 1

6 2 6 2

7 3 7 3

4 0 4 0

5 1 5 1

6 2 6 2

7 3 7 3

4 0 4 0

5 1 5 1

6 2 6 2

7 3 7 3

A23-16 A15-8 A7-0 M7-0 Dummy Byte1 Byte2

4 0

5 1

6 2

7 3

Byte3

Quad I/O Word Fast Read with “8/16/32/64-Byte Wrap Around” in Standard SPI mode

The Quad I/O Word Fast Read command can be used to access a specific portion within a page by issuing “Set

Burst with Wrap” (77H) commands prior to E7H. The “Set Burst with Wrap” (77H) command can either enable

or disable the “Wrap Around” feature for the following E7H commands. When “Wrap Around” is enabled, the

data being accessed can be limited to either an 8/16/32/64-byte section of a 256-byte page. The output data

starts at the initial address specified in the command, once it reaches the ending boundary of the 8/16/32/64-byte

section, the output will wrap around the beginning boundary automatically until CS# is pulled high to terminate

the command.

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 multiple read commands.

The “Set Burst with Wrap” command allows three “Wrap Bits” W6-W4 to be set. The W4 bit is used to enable

or disable the “Wrap Around” operation while W6-W5 is used to specify the length of the wrap around section

within a page.

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