Serial Peripheral Interface (SPI) protocol establishes synchronous-serial bit transfer between different ICs. It follows master-slave relationship, with master sharing a clock signal with the slave IC for ensuring synchronous transfers.
Source : Wikipedia
This repository contains three blocks required for implementing the SPI interface, i.e. SPI-Master, SPI-Slave and a top wrapper acting as a Register Interface (RIF)
Clock polarity: Shared clock (sclk) remains low under idle condition.
Fig 1: Transmitting and receiving two values ('d161 & 'd121) via SPI interface.