Editing Serial Peripheral Interface (section)

=== Three-wire ===
Three-wire variants of SPI restricted to a [[half-duplex]] mode use a single bidirectional data line called SISO (slave out/slave in) or MOMI (master out/master in) instead of SPI's two unidirectional lines (MOSI and MISO). Three-wire tends to be used for lower-performance parts, such as small EEPROMs used only during system startup, certain sensors, and [[Serial Peripheral Interface#Microwire|Microwire]]. Few SPI controllers support this mode, although it can be easily [[Bit-banging|bit-banged]] in software.