tiva C Launchpad Clock tree tool

We're glad to you hear you're considering the Launchpad for use in your classroom.  It's a great platform to learn embedded development on since it can scale from blinking LED's to controlling servos to being a USB device.  Of course, we may be a little biased.  In any case, hopefully your students will enjoy it!

With respect to the Tiva LM4F clock "tree", it's relatively simple as there are not really any clock muxes or dividers when fanning the clock out to the various peripherals.  This tree has no branches.

There are different oscillator sources which impact the overall clock speed but, with only a few exceptions, that one clock goes everywhere within the part.

With the PLL enabled you can set dividers to achieve clock rates from 16MHz through 80MHz.

With the PLL disabled you can derive your clock from PIOSC which is fixed at 16MHz (ignoring trim details and variation over temperature).  The µC comes out of reset running off PIOSC so you can probably start writing and running code and tackle 90% of your work without even worrying about the clock.

If power is a concern you also have the LFIOSC which runs at ~33KHz.  LFIOSC is meant for hibernating and entering very low power states at the expense of latency when entering higher states.

There are a few peripherals (ADC, SSI, UART) that have an ALTCLK select (derived from PIOSC @ 16MHz) while the rest of the part runs off SYSCLK (typically 80MHz).  This allows you to enter a lower power state (stop the PLL) and still be able to interact with, say, your UART without the time-base of the baud clock changing.  BUT a 16MHz clock source will only divide up to about 921,600 bps. 

Whenever you run with multiple clock domains you should comb through the errata to make sure you don't get stuck on a clock domain crossing bug.

So... the simplified model:  SYSCLK @ 40 or 80MHz (typically) and ALTCLK @ 16 MHz with three peripherals that can be switched to ALTCLK.

To answer your specific question: we don't have a tool for clock configuration nor is one on the road map at the moment.

Good luck!

--Miles

Hi Miles,

Thank you for the information.  No the only reason I was asking about a clock tool was that it might be easier for them to get their head around it all.  Without the need to be teaching them all of it.

I do however really enjoy your thorough and simple explanation of how it all works.

Thanks

Warwick