SPI vs QSPI: Key Differences Explained

This article clarifies the differences between SPI (Serial Peripheral Interface) and QSPI (Queued Serial Peripheral Interface), presenting a comparison in a tabular format. We’ll explore key aspects like interface diagrams, data rates, distance limitations, and the advantages and disadvantages of each.

SPI Explained

• Master-Slave Configuration: Operates in master-slave configurations, supporting one master and one slave, or one master and multiple slaves.
• Synchronous Interface: Employs a clock signal generated by the master device, making it a synchronous interface.
• Duplex Modes: Supports both half-duplex and full-duplex communication modes.
• Communication Lines: Utilizes four primary lines:
  • MOSI (Master Out Slave In)
  • MISO (Master In Slave Out)
  • SCLK (Serial Clock)
  • CS (Chip Select) or SS (Slave Select)
• Data Rate: Typically supports data rates ranging from 10 Mbps to 20 Mbps.
• Device Addressing: Lacks device addressing capabilities, unlike I2C.
• Acknowledgement: Doesn’t incorporate a mechanism for acknowledging data receipt, unlike I2C.
• Advantages and Disadvantages: For a more detailed overview, refer to resources outlining the Pros and Cons of SPI Interface.

QSPI Explained

Image Courtesy: STMicroelectronics

• Controller Extension: QSPI serves as a controller extension to the standard SPI bus.
• Queued Operation: Leverages a data queue with pointers, enabling data transfers without direct CPU intervention.
• Wrap-Around Mode: Features a wrap-around mode that facilitates continuous data transfer to and from the queue without constant CPU involvement.
• Memory-Mapped Device: In QSPI, the peripheral essentially acts as a memory-mapped parallel device for the CPU.
• Applications: Commonly used to control ADC (Analog-to-Digital Converter) devices.
• Additional Features: Includes chip select and transfer length delay functionalities.
• Quad SPI: QSPI also represents Quad SPI.

SPI vs QSPI: A Comparison Table