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
Formule
## 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.
Exemple Résolu
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%
Questions Fréquentes
What limits SPI clock speed?
The slave device datasheet specifies the maximum clock. PCB layout, cable length, and signal integrity also limit practical speed.
Is SPI faster than I2C?
Generally yes. SPI runs at 10+ MHz while standard I2C is 100/400 kHz. SPI also has lower overhead per byte.
Can I use SPI with multiple devices?
Yes, using separate chip-select lines for each device. All devices share the clock and data lines.
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