[PATCH 2/2] bsp/lm4f120: new BSP to support TI LM4F120 XL LaunchPad board
karel.gardas at centrum.cz
Mon Aug 19 18:40:22 UTC 2013
first of all sorry for delay, my answers are in text below.
On 08/14/13 11:49 PM, Eugeniy Meshcheryakov wrote:
> 14 серпня 2013 о 16:54 +0200 Karel Gardas написав(-ла):
>> What makes me more nervous about supporting older chips is addition:
>> rcc&= SYSCONRCC_MOSCDIS;
>> syscon->rcc = rcc;
> Ugh, wait, you are clearing all bits but SYSCONRCC_MOSCDIS in RCC? That
> could not be right. Did you mean to do
> rcc&= ~SYSCONRCC_MOSCDIS;
No, I mean exactly what's there. What's the problem with disabling main
oscillator here? i.e. to disable main oscillator you need to set MOSCDIS.
>> ^ w/o this my code is not running at all, i.e. it probably runs on
>> default 12 MHz. I'm curious how older chips worked without this.
> The switching to PLL procedure for lm3s3749 does not mention MOSCDIS
> bit. In fact, it is only mentioned in the register description, but not
> anywhere else in the datasheet. I guess it should be safe to clear it,
> but I cannot test this on the real hardware till next week.
it would be great if you test that since I would rather prefer not to
break your code on your board(s) :-)
BTW, LM4F120 spec adds following important note on page 219:
When transitioning the system clock configuration to use the MOSC as the
clock source, the MOSCDIS bit must be set prior to reselecting the MOSC
or an undefined
system clock configuration can sporadically occur.
so I think that's what you are missing in LM3 spec.
Please let me know if the code runs for you.
Thanks a lot for your testing!
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