Question about PLL and External Crystal

The PLLFREQ0 and PLLFREQ1 registers are read-only.

You may not set your own MINT, MFRAC, Q or N values.

11Mhz is not a supported crystal frequency, per table 23-10.

--Miles

But when i read file sysctl.h, in this file have the define MINT, MFRAC, Q and N value. I want know may i set these value?

And i have a question about crystal, is the baudrate error in UART mode  crystal dependence?

Thanks. 

There are definitions for reading and shifting those bitfields but those fields are read only.  You can not write to them.

If you use an unsupported crystal then the PLL will not operate at the expected speed of 400MHz.  Every clock derived from the PLL will, as a result, be wrong.  This would affect the UART since the BAUD clock will be incorrect.

Thanks your information.

In UART mode, how to calculation the baudrate error? How BRD to have connection with baudrate error? 

You can't.  You must use a supported crystal.  That's the only way to guarantee the system will operate properly.

When using a supported crystal and setting the proper divider wth SysCtlClockSet() you will know the exact clock frequency and there will be no baud rate discrepancy when setting the BRD.  If you use the wrong crystal ALL your peripherals will have a bad clock (and not all peripherals have a programmable divisor).

Thanks your information.