FPGA implementation of I2C & SPI protocols: A comparative study

I²C and SPI are the most commonly used serial protocols for both inter-chip and intra-chip low/medium bandwidth data-transfers. This paper contrasts and compares physical implementation aspects of the two protocols through a number of recent Xilinx´s FPGA families, showing up which protocol features are responsible of substantial area overhead. This valuable information helps designers to make careful and tightly tailored architecture decisions. For a comprehensive comparative study, both protocols are implemented as general purpose IP solutions, incorporating all necessary features required by modern ASIC/SoC applications according to a recent market investigation of an important number of commercial I²C and SPI devices. The RTL code is technology independent, inducing around 25% area overhead for I²C over SPI, and almost the same delays for both designs.