The QSPI operates in one of two modes regarding the generation of the serial clock and slave select signals: master or slave mode. The master generates and drives the clock and select signals, the slave receives these signals.

The QSPI operates in one of three modes regarding the direction of the communication and depending whether the transmission and the reception appear simultaneously or not: duplex, half-duplex and simplex mode.

Figure 1. Operating modes overview

This gives six possible combinations for the operating mode of the QSPI: master duplex, half-duplex, and simplex; slave duplex, half-duplex, and simplex.

Note: The half-duplex mode can be implemented either by direct connection between two different pins on the pcb, one data output and one data input pin, or by using single pins mapped to both data input and data output signals. See the pinning and port chapters for the pinning definition of a particular product. The module itself does not differentiate between the full-duplex, half-duplex or simplex connection.

Figure 2. Operating modes and types of connections