Calcolatore Latenza Interrupt
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Typically 16 for UART
Baud Rate Divider
9
Baud Rate Divider vs Peripheral Clock
Formula
## UART Baud Rate Generation UART baud rate is derived from the peripheral clock using an integer divider and oversampling. ### Formula **Divider = round(Clock / (Oversampling x Baud Rate))** **Actual Baud = Clock / (Oversampling x Divider)** **Error = |Actual - Desired| / Desired x 100%** Baud rate error should stay below 2% for reliable communication. Errors above 3-5% cause framing errors, especially for multi-byte transfers.
Esempio Risolto
16 MHz clock, 115200 baud, 16x oversampling.
- 01Exact divider: 16e6 / (16 x 115200) = 8.68
- 02Integer divider: round(8.68) = 9
- 03Actual baud: 16e6 / (16 x 9) = 111,111 baud
- 04Error: |111111 - 115200| / 115200 = 3.55%
- 05This is marginal; consider a different clock frequency
Domande Frequenti
What baud rate error is acceptable?
Below 2% is safe. At 3%+ errors accumulate over a byte (10 bits) and the last bits may be sampled incorrectly.
How do I reduce baud rate error?
Use a clock frequency that divides evenly into common baud rates. 14.7456 MHz and 11.0592 MHz give zero error at standard rates.
What is oversampling in UART?
The receiver samples each bit multiple times (typically 16x) and uses the middle samples for data recovery, improving noise immunity.
Impara