Enter your System Clock Frequency and Clock Prescaler to calculate your SPI Clock Frequency, Clock Period, and Transfer Time — then add Data Bits per Transfer, Data Transfer Rate, and Protocol Overhead to see your Maximum Bit Rate and real-world Effective Throughput after accounting for bus overhead.
SPI Clock Frequency
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Maximum Bit Rate
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Effective Throughput
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Clock Period
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Transfer Time
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SPI clock frequency determines how fast data can be transmitted over the Serial Peripheral Interface bus. It's calculated by dividing the system clock by a prescaler value and directly affects the maximum data throughput of your SPI communication.
Choose the prescaler based on your slave device's maximum supported SPI frequency and signal integrity requirements. Higher frequencies allow faster data transfer but may cause issues with long traces or slower slave devices.
Effective throughput is reduced by protocol overhead including chip select setup/hold times, inter-byte delays, and processing time between transfers. Real-world throughput is typically 80-95% of the theoretical maximum.
The calculated frequency is the maximum theoretical speed based on your system clock and prescaler. Running faster would require a higher system clock or lower prescaler value if supported by your microcontroller.
Wider data transfers (16-bit, 32-bit) can improve efficiency by reducing the number of individual transfers needed, but the actual benefit depends on your application's data structure and the SPI controller's capabilities.
Bit rate is the raw speed of data transmission, while throughput accounts for protocol overhead and actual usable data transfer rate. Throughput is always lower than bit rate due to control signals and timing requirements.