64 lines
2.0 KiB
Plaintext
64 lines
2.0 KiB
Plaintext
/** CMU convenience functions
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*
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* These functions assist in clock switching, and are intended to be safer to
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* use than direct fiddling with registers. They try to be suitable for typical
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* applications, and will invest some bytes of code in order to minimize power
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* consumption.
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*
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* @todo Work on this module is stalled until I can figure out if there is a
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* way to have a cmu_shutdown_unused function at all.
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*
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* @defgroup EFM32TG_CMU_convenience CMU convenience functions
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* @{
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*/
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/** Disable all oscillators not currently in use.
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*
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* The implementation follows d0034_efm32tg_reference_manual.pdf figure 11.1.
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* The clock out pin configurations are not depicted there, but described in
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* section 11.3.4.
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*
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* @todo This function is ignorant of ongoing calibrations.
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*
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* @todo This doesn't work at all: Fields like HFCLKSEL are write-only.
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* */
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static void cmu_shutdown_unused(void)
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{
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/* Is HFXO needed? */
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if (!(
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(CMU_CMD & CMU_CMD_HFCLKSEL_MASK) == CMU_CMD_HFCLKSEL_HFXO ||
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(
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(CMU_CTRL & CMU_CTRL_CLKOUTSEL1_MASK) == CMU_CTRL_CLKOUTSEL1_HFXOQ &&
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(CMU_ROUTE & CMU_ROUTE_CLKOUT1PEN)
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) || (
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(CMU_CTRL & CMU_CTRL_CLKOUTSEL0_MASK) == CMU_CTRL_CLKOUTSEL0_HFXO &&
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(CMU_ROUTE & CMU_ROUTE_CLKOUT0PEN)
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)))
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CMU_OSCENCMD = CMU_OSCENCMD_HFXODIS;
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/* Is HFRCO neede? */
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if (!(
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(CMU_CMD & CMU_CMD_HFCLKSEL_MASK) == CMU_CMD_HFCLKSEL_HFRCO ||
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(
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(CMU_CTRL & CMU_CTRL_CLKOUTSEL1_MASK) == CMU_CTRL_CLKOUTSEL1_HFRCOQ &&
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(CMU_ROUTE & CMU_ROUTE_CLKOUT1PEN)
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) || (
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(CMU_CTRL & CMU_CTRL_CLKOUTSEL0_MASK) == CMU_CTRL_CLKOUTSEL0_HFRCO &&
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(CMU_ROUTE & CMU_ROUTE_CLKOUT0PEN)
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)))
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{}
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// CMU_OSCENCMD = CMU_OSCENCMD_HFRCODIS;
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}
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/** Switch HFCLK to LFRC. This call is not only blocking, but even freezes
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* everything depending on HFCLK until LFRC is stable. The procedure is
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* sketched in d0034_efm32tg_reference_manual.pdf figure 11.2. */
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static void cmu_hfclk_switch_blocking(void)
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{
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CMU_OSCENCMD = CMU_OSCENCMD_LFRCOEN;
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CMU_CMD = CMU_CMD_HFCLKSEL_LFRCO;
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CMU_OSCENCMD = CMU_OSCENCMD_HFRCODIS;
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}
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/** @} */
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