SPI Data Rate Calculator
Calculate SPI bus data throughput from clock speed and transfer parameters.
CS assertion/deassertion overhead
Raw Data Rate
1.00 MB/s
Raw Data Rate vs SPI Clock Speed
SPI Data Rate
SPI (Serial Peripheral Interface) transfers one bit per clock cycle. The effective rate depends on clock speed and protocol overhead.
Formulas
Raw Rate = Clock Speed / 8 (bytes per second)
Effective Rate = Clock x Data Bits / (Data Bits + Idle) / 8
Idle clocks account for chip-select toggling and inter-transfer gaps. SPI has no addressing overhead unlike I2C, making it faster for bulk transfers.
Example Calculation
8 MHz SPI clock, 8-bit transfers, 2 idle clocks between transfers.
- 01Raw rate: 8e6 / 8 = 1.00 MB/s
- 02Clocks per transfer: 8 + 2 = 10
- 03Effective rate: 8e6 x 8 / 10 / 8 = 0.80 MB/s
- 04Bus efficiency: 8 / 10 = 80%
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