SPI

 What is SPI?

SPI was developed by Motorola (now part of NXP Semiconductors) around 1985. It is a synchronous serial interface intended for communication between devices over short distances. Since then, it has become a de-facto standard used by many semiconductor manufacturers, especially in microprocessors and microcontrollers.

The reason for the popularity of SPI lies in its many advantages. The first is that it is a simple hardware addressed interface that offers complete flexibility for the number of bis transferred. It uses a master-slave model with a single master and can handle multiple slave devices using duplex communications operating at clock speeds of up to 50 MHz. It does not use a standard protocol and transfers only data packets, making it ideal for transferring. long data streams.

SPI uses a maximum of four signal lines (Figure 1). The master device, usually a processor or controller, supplies and controls the clock (SCK) and chip select lines (CS). The entire multiplexer operation is handled via the Master Out Slave In (MOSI) and Master In Slave Out (MISO) data lines. In a simple individual master, with individual secondary device configuration, the chip selection line can be removed and CS input to the secondary device can be forced to the logical enabled state. If the secondary device can only send data (half-duplex communication), then the MOSI line can also be removed, thus reducing the signal count further. The data is output through the clock signal in such a way that the data transfer resembles a shift register with one bit changed for each clock.