Quad-SPI interface (QUADSPI) RM0351
412/1693 DocID024597 Rev 3
Figure 55. nCS when CKMODE = 1 in SDR mode (T = CLK period)
When CKMODE = 1 (“mode3”) and DDRM = 1 (DDR mode), nCS falls one CLK cycle
before an operation first rising CLK edge, and nCS rises one CLK cycle after the operation
final active rising CLK edge, as shown in Figure 56. Because DDR operations must finish
with a falling edge, CLK is low when nCS rises, and CLK rises back up one half of a CLK
cycle afterwards.
Figure 56. nCS when CKMODE = 1 in DDR mode (T = CLK period)
When the FIFO stays full in a read operation or if the FIFO stays empty in a write operation,
the operation stalls and CLK stays low until firmware services the FIFO. If an abort occurs
when an operation is stalled, nCS rises just after the abort is requested and then CLK rises
one half of a CLK cycle later, as shown in Figure 57.
Figure 57. nCS when CKMODE = 1 with an abort (T = CLK period)
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