There are multiple I/O interfacing options.
Single Device Interface
The single device mode supports 1-bit, 2-bit, and 4-bit bus widths. This mode also supports 24-bit addressing and 32-bit addressing modes. This mode also supports 24-bit addressing and 32-bit addressing modes. The single device mode is a common setup because it is low cost and has a lower pin count boot and configuration.
Two QSPI devices share the same bus in QSPI dual-stacked mode to double the maximum addressable flash memory storage for the application. This mode also reduces the boot interface I/O pin count because the bus is shared and only one additional interface pin is needed for the flash select. In this mode, only the lower QSPI addressable flash memory space can be used for boot and the throughput remains the same as it is in the QSPI single-device mode.
The QSPI dual-parallel mode increases performance by combining two QSPI devices with 4-bit data widths to create an 8-bit data bus width. The QSPI dual-parallel mode only supports each QSPI device in a 4-bit data bus width. The QSPI dual-parallel mode does not support QSPI devices in 1-bit or 2-bit data bus widths.
The following figure shows the QSPI flash interface options.
QSPI Example Read Waveform
The following figure shows an example QSPI read waveform with the relative sequence of events.