GD25B64CSIG datasheet(24/57 Pages) GIGADEVICE

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3.3V Uniform Sector

Dual and Quad Serial Flash

GD25B64C

Figure 15. Quad I/O Word Fast Read Sequence Diagram (M5-4= (1, 0))

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.

7.13.

Set Burst with Wrap (77H)

The Set Burst

with Wrap command is used in conjunction with “Quad I/O Fast Read” and “Quad I/O Word Fast Read”

command to access a fixed length of 8/16/32/64-byte section within a 256-byte page.

The Set Burst with Wrap command sequence: CS# goes low  Send Set Burst with Wrap command  Send 24

dummy bits 

Send 8 bits “Wrap bits”  CS# goes high.

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

If the W6-W4 bits are set by the

Set Burst with Wrap command, all the following “Quad I/O Fast Read” and “Quad I/O

Word Fast Read” command will use the W6-W4 setting to access the 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 command should be issued to set

W4=1.

CS#

SCLK

9 10 11 12 13 14 15

IO0

IO1

IO2

IO3

A23-16 A15-8 A7-0

M7-0 Dummy Byte1 Byte2

Byte3

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