W25Q16V Datasheet, PDF (26/60 Pages) Winbond – 16M-BIT SERIAL FLASH MEMORY WITH DUAL AND QUAD SPI

W25Q16V
10.2.12 Fast Read Dual I/O (BBh)
The Fast Read Dual I/O (BBh) instruction allows for improved random access while maintaining two IO
pins, IO₀ and IO₁. It is similar to the Fast Read Dual Output (3Bh) instruction but with the capability to
input the Address bits (A23-0) two bits per clock. This reduced instruction overhead may allow for code
execution (XIP) directly from the Dual SPI in some applications.
Fast Read Dual I/O with “Continuous Read Mode”
The Fast Read Dual 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 12a. The
upper nibble of the (M7-4) controls the length of the next Fast Read Dual 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 (M7-0) equals “Ax” hex, then the next Fast Read Dual I/O instruction
(after /CS is raised and then lowered) does not require the BBh instruction code, as shown in figure 12b.
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 (M7-0) are any value other than
“Ax” hex, 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 be used to
reset (M7-0) before issuing normal instructions (See 10.2.29 for detailed descriptions).
Figure 12a. Fast Read Dual Input/Output Instruction Sequence Diagram (M7-0 = 0xh or NOT Axh)
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