The Serial Peripheral Interface is used to transfer data between integrated circuits using a reduced number of data lines. This article provides the background information needed for novices to understand the interface.

Related Information

Serial Peripheral Interface (SPI) Full duplex, synchronous serial data transfer Data is shifted out of the master's (mega128) MOSI pin and in it's MISO pin Data transfer is initiated by simply writing data to the SPI data register. All data movement is coordinated by SCK. Slave select may or may not be used depending on interfacing device.
Serial Peripheral Interface (SPI) is a synchronous serial data protocol used by microcontrollers for communicating with one or more peripheral devices quickly over short distances. It can also be used for communication between two microcontrollers. With an SPI connection there is always one master.
Serial Peripheral Interface (SPI) is an interface bus commonly used to send data between microcontrollers and small peripherals such as shift registers, sensors, and SD cards. It uses separate clock and data lines, along with a select line to choose the device you wish to talk to. A common serial.
Serial Peripheral Interface Basics. The SPI communication stands for serial peripheral interface communication protocol, which was developed by the Motorola in 1972. SPI interface is available on popular communication controllers such as PIC, AVR, and ARM controller, etc. It has synchronous serial communication data link that operates in full.

No preview available for pdf. The three most common multi-wire serial data transmission formats that have been in use for decades are I²C, UART, and SPI. This article looks at the Serial Peripheral Interface (SPI) Bus, which has escaped explicit standardization, so always check the datasheet of the integrated circuit that you are working with before you implement the protocol.

Capabilities and Characteristics

The Serial Peripheral Interface Bus provides full-duplex synchronous communication between a master device and a slave using four data lines.

Basic Master-Slave Configuration

The Serial Peripheral Interface allows bits of data to be shifted out of a master device into a slave, and at the same time, bits can be shifted out of the slave into the master.

Serial Peripheral Interface (SPI) is an interface bus commonly used to send data between microcontrollers and small peripherals such as shift registers, sensors, and SD cards. It uses separate clock and data lines, along with a select line to choose the device you wish to talk to. A common serial.

Animation 1 shows data shifted out of Microchip A into Microchip B, and from Microchip B into Microchip A.

Animation 2 shows a virtual 4-channel oscilloscope trace of an SPI transaction between two microchips. Created with Mathematica by Mark Hughes

As SPI is not standardized, it is possible to encounter situations where either the Most Significant Bit (MSb) or the Least Significant Bit (LSb) is transferred first. Check the datasheet for your device and set up your identifies it as an active-low signal). Controlled by the master device. An active slave-select line indicates that the master is sending data to or requesting data from the corresponding slave device.

MOSI: Master Out ⇒ Slave In. Data leaves the master device and enters the slave device. MOSI lines on chip A are connected to MOSI lines on chip B.

MISO: Master In ⇐ Slave Out. Data leaves the slave device and enters the master device (or another slave, in a daisy-chain configuration; see the next section). MISO lines on chip A are connected to MISO lines on chip B.

CPOL: Clock Polarity. This governs the initial logic state of the clock signal. Refer to the previous section for more information.

CPHA: Clock Phase. This governs the relationship between the data transitions and the clock transitions. Refer to the previous section for more information.

Slave Select and Daisy Chain

Multiple-Slave-Select Configuration

Serial Peripheral Interface Protocol Ppt

In the standard SPI arrangement, the master device can write data to or request data from individual devices that share common data lines by enabling the device, i.e., by setting the slave-select line of the corresponding device to logic low. Care should be taken not to enable multiple slaves simultaneously, as the data returned to the master will be corrupted by driver contention between the MISO lines. Certain applications do not require data to be returned to the master; in such cases, multiple slaves can be addressed simultaneously if the master wants to send the same data to multiple slaves.

In the multiple-slave-select configuration, each slave requires a unique slave-select line from the master. If the master does not have enough I/O pins for the required number of slaves, I/O expansion can be implemented by incorporating a decoder/demultiplexer, such as the 74HC(T)238 (PDF) (3-to-8 line decoder/demultiplexer).

Serial Peripheral Interface Standard

Daisy-Chain Configuration

In this configuration, data moves from one device to the next. The final slave device can return data to the master.

In the daisy-chain configuration, all slaves share a common slave-select line. Data is shifted out of the master into the first slave, and then out of the first slave into the second, and so on. The data cascades down the line until the last slave in the series, which can then use its MISO line to send data to the master device.

This configuration would be well suited to the individually addressable LED light strings that are popular during the holidays.

Conclusion

The Serial Peripheral Interface has been around for decades, and there is no reason to expect it to go away anytime soon. While I²C and UART might enjoy more popularity, SPI is a versatile and straightforward serial-communications interface that is excellent for certain applications.