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W25Q40BL

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7.2.15 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

clock are required 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.

Fast Read Quad I/O with “Continuous Read Mode”

The Fast Read Quad I/O instruction can further reduce instruction overhead through setting the

“Continuous Read Mode” bits (M7-0) after the input Address bits (A23-0), as shown in figure 14a. The

upper nibble of the (M7-4) controls the length of the next Fast Read Quad I/O instruction through the

inclusion or exclusion of the first byte instruction code. The lower nibble bits of the (M3-0) are don’t care

(“x”). However, the IO pins should be high-impedance prior to the falling edge of the first data out clock.

If the “Continuous Read Mode” bits M5-4 = (1,0), then the next Fast Read Quad I/O instruction (after /CS

is raised and then lowered) does not require the EBh instruction code, as shown in figure 14b. This

reduces the instruction sequence by eight clocks and allows the Read address to be immediately entered

after /CS is asserted low. If the “Continuous Read Mode” bits M5-4 do not equal to (1,0), the next

instruction (after /CS is raised and then lowered) requires the first byte instruction code, thus returning to

normal operation. A “Continuous Read Mode” Reset instruction can also be used to reset (M7-0) before

issuing normal instructions (See 7.2.20 for detail descriptions).

Byte 1

Byte 2

Byte 1

Byte 2

Figure 14a. Fast Read Quad I/O Instruction Sequence (Initial instruction or previous M5-4

≠ 10)

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