GD25Q21 Datasheet, PDF (24/49 Pages) ELM Electronics – Uniform Sector Dual and Quad Serial Flash

GD25Q21BxIGx Uniform Sector Dual and Quad Serial Flash
http://www.elm-tech.com
Figure 17. Quad I/O Word Fast Read Sequence Diagram (M7-0 = AXH)
CS#
SCLK
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
SI(IO0)
SO(IO1)
WP#(IO2)
HOLD#(IO3)
40404040
404040 4
51515151
515151 5
62626262
626262 6
73737373
737373 7
A23-16 A15-8 A7-0 M7-0 Dummy Byte1 Byte2 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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