63.8.3.10 Mode Fault Detection

The SPI has the capability to operate in multi-host environment. Consequently, the NPCS0/NSS line must be monitored. If one of the hosts on the SPI bus is currently transmitting, the NPCS0/NSS line is low and the SPI must not transmit a data. A mode fault is detected when the SPI is programmed in Host mode and a low level is driven by an external host on the NPCS0/NSS signal. In multi-host environment, NPCS0, MOSI, MISO and SPCK pins must be configured in open drain (through the PIO controller). When a mode fault is detected, the FLEX_SPI_SR.MODF bit is set until FLEX_SPI_SR is read and the SPI is automatically disabled until it is re-enabled by writing the FLEX_SPI_CR.SPIEN bit to 1.

By default, the mode fault detection is enabled. The user can disable it by setting the FLEX_SPI_MR.MODFDIS bit.