i.MX 6Solo/6DualLite Applications Processors for Consumer Products, Rev. 2.1
20 Freescale Semiconductor
Modules List
3.1 Special Signal Considerations
Table 3 lists special signal considerations for the i.MX 6Solo/6DualLite processors. The signal names are
listed in alphabetical order.
The package contact assignments can be found in Section 6, “Package Information and Contact
Assignments.” Signal descriptions are provided in the i.MX 6Solo/6DualLite Reference Manual
(IMX6SDLRM).
Table 3. Special Signal Considerations
Signal Name Remarks
CLK1_P/CLK1_N
CLK2_P/CLK2_N
Two general purpose differential high speed clock Input/outputs are provided.
Any or both of them could be used:
• To feed external reference clock to the PLLs and further to the modules inside SoC, for example
as alternate reference clock for PCIe, Video/Audio interfaces, etc.
• To output internal SoC clock to be used outside the SoC as either reference clock or as a
functional clock for peripherals, for example it could be used as an output of the PCIe master
clock (root complex use)
See the i.MX 6Solo/6DualLite reference manual for details on the respective clock trees.
The clock inputs/outputs are LVDS differential pairs compatible with TIA/EIA-644 standard, the
maximum frequency range supported is 0...600 MHz.
Alternatively one may use single ended signal to drive CLKx_P input. In this case corresponding
CLKx_N input should be tied to the constant voltage level equal 1/2 of the input signal swing.
Termination should be provided in case of high frequency signals.
See LVDS pad electrical specification for further details.
After initialization, the CLKx inputs/outputs could be disabled (if not used). If unused any or both of
the CLKx_N/P pairs may be left floating.
XTALOSC_RTC_XTALI/
RTC_XTALO
If the user wishes to configure XTALOSC_RTC_XTALI and RTC_XTALO as an RTC oscillator, a
32.768 kHz crystal, (100 k ESR, 10 pF load) should be connected between
XTALOSC_RTC_XTALI and RTC_XTALO. Keep in mind the capacitors implemented on either side
of the crystal are about twice the crystal load capacitor. To hit the exact oscillation frequency, the
board capacitors need to be reduced to account for board and chip parasitics. The integrated
oscillation amplifier is self biasing, but relatively weak. Care must be taken to limit parasitic leakage
from XTALOSC_RTC_XTALI and RTC_XTALO to either power or ground (>100 M). This will
debias the amplifier and cause a reduction of startup margin. Typically XTALOSC_RTC_XTALI and
RTC_XTALO should bias to approximately 0.5 V.
If it is desired to feed an external low frequency clock into XTALOSC_RTC_XTALI the RTC_XTALO
pin should be left floating or driven with a complimentary signal. The logic level of this forcing clock
should not exceed VDD_SNVS_CAP level and the frequency should be <100 kHz under typical
conditions.
In case when high accuracy real time clock are not required system may use internal low frequency
ring oscillator. It is recommended to connect XTALOSC_RTC_XTALI to GND and keep
RTC_XTALO floating.
XTALI/XTALO A 24.0 MHz crystal should be connected between XTALI and XTALO. level and the frequency
should be <32 MHz under typical conditions.
The crystal must be rated for a maximum drive level of 250 W. An ESR (equivalent series
resistance) of typical 80 is recommended. Freescale BSP (board support package) software
requires 24 MHz on XTALI/XTALO.
The crystal can be eliminated if an external 24 MHz oscillator is available in the system. In this
case, XTALI must be directly driven by the external oscillator and XTALO is floated. The XTALI
signal level must swing from ~0.8 x NVCC_PLL_OUT to ~0.2 V.
If this clock is used as a reference for USB and PCIe, then there are strict frequency tolerance and
jitter requirements. See OSC24M chapter and relevant interface specifications chapters for details.