W25Q256JVEIQ-TR Datasheet, PDF (48/92 Pages) Winbond – 3V 256M-BIT SERIAL FLASH MEMORY WITH DUAL/QUAD SPI

W25Q256JV
8.2.20 Fast Read Quad I/O (EBh)
The Fast Read Quad I/O (EBh) instruction is similar to the Fast Read Dual I/O (BBh) instruction except
that address and data bits are input and output through four pins IO0, IO1, IO2 and IO3 and four Dummy
clocks are required in SPI mode prior to the data output. The Quad I/O dramatically reduces instruction
overhead allowing faster random access for code execution (XIP) directly from the Quad SPI. The Quad
Enable bit (QE) of Status Register-2 must be set to enable the Fast Read Quad I/O Instruction.
/CS
CLK
Mode 3
Mode 0
IO₀
IO₁
IO₂
IO₃
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Instruction (EBh)
A23-16 A15-8
20 16 12 8
A7-0
40
M7-0
40
Dummy Dummy
4
IOs switch from
Input to Output
0404
21 17 13 9 5 1 5 1
51515
22 18 14 10 6 2 6 2
62626
23 19 15 11 7 3 7 3
73
Byte 1
73
Byte 2
7
Byte 3
Figure 26a. Fast Read Quad I/O (M7-M0 should be set to FFh)
32-Bit Address is required when the device is operating in 4-Byte Address Mode
Fast Read Quad I/O with “8/16/32/64-Byte Wrap Around” in Standard SPI mode
The Fast 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) command prior to EBh. The “Set Burst with Wrap” (77h) command can
either enable or disable the “Wrap Around” feature for the following EBh commands. When “Wrap
Around” is enabled, the data being accessed can be limited to either an 8, 16, 32 or 64-byte section of a
256-byte page. 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 will wrap around to 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” 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 are used to specify the length of the wrap
around section within a page. Refer to section 8.2.24 for detail descriptions.
- 47 -