Are there any tools available to help selecting the crystal and PLL settings
for standard baud rates, and specifically the higher ones, up to 921600 baud?
Minimum bus clock required for 921600 is 921600*16=14745600Hz.
You may use standard UART crystal frequencies like 3.6864MHz or 7.3728MHz and PLL multiply it to 14.7456MHz. Processor expert may help finding right PLL/FLL settings.
I am having same problem and until now I have no solution. Only an external resonator on 29,4912 MHz (BUS clock will be 14,7456 MHz) http://cz.farnell.com/abracon/asem1-29-4912mhz-lc-t/mems-oscillator-29-4912mhz-smd/dp/1633615 But I will also be glad for some crystal and FLL solution if somebody has it.
now I already upgrade my hardware with external oscillator of 29.4912 MHz and run it as clock source by code:
// 29.4912MHz Oscillator
// Fbus = ( Fext * 1 / BDIV ) / 2 => 14.7456MHz
ICSC2_BDIV = 0b00; // 00 BDIV = 1
ICSC2_LP = 1; // 1 FLL is disabled in bypass modes
ICSC2_EREFS = 0; // 0 External Clock Source requested.
// wait for stability of oscillator
for ( i = 0 ; i < 10000 ; i++ );
ICSC1_IREFS = 0; // 0 External reference clock selected.
ICSC1_CLKS = 0b10; // 10 External reference clock is selected
My baud rate is 921600. I am using MC9S08QE16 device.
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