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SPI Clock Calculator
Calculate MCU SPI clock settings from peripheral clock, target SCLK, and available prescalers. Check actual frequency, frequency error, bit time, and slave clock limit.
Input Parameters
Results
Equations Used
Actual SPI Clock: Fspi = Fsource / Prescaler
Error: Error % = (Factual - Ftarget) / Ftarget × 100%
Clock Period: T = 1 / Fspi
Available Prescalers: 2, 4, 8, 16, 32, 64, 128, 256
Frequently Asked Questions (FAQ)
Q1: What does an SPI clock calculator do?
It finds the actual SPI clock produced by common MCU prescaler settings and compares it with a target clock.
Q2: Why is my actual SPI frequency different from the target?
MCUs usually offer only discrete clock dividers, so the exact target frequency may not be available.
Q3: Should SPI clock stay below the slave maximum?
Yes. The selected SPI clock should not exceed the maximum SCLK specified by the slave datasheet.
Q4: What is the safest selection mode?
The 'not exceeding target' mode is usually safer when a device has a strict maximum clock limit.
Q5: Does this include setup and hold timing?
No. Check SPI mode, propagation delay, cable length, PCB routing, setup/hold timing, and logic voltage levels separately.
