emCON-MX8MM - Hardware Manual (Rev1)
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4.1.1
Processor Clocks
The 24 MHz main clock is generated by a quartz crystal. The internal PLLs multiply the 24 MHz main
clock to the internal clocks. All clocks within the processor are derived from theses frequencies, via
various software configurable dividers.
The core clock can run up to 1,8 GHz. For power management, the core clock can be varied.
It must be considered that the core voltage should be adapted if the core frequency is varied.
More information about the i.MX8MM clock system is described in the CCM chapter of the
i.MX8MM Reference Manual [1].
The RTC_XTALI clock input of the CPU is supplied by a 32,768 kHz clock, generated by the PMIC and
used for the internal low speed clocks. The PMIC generates the clock signal by an external 32,768
kHz quartz crystal.
An additional I²C RTC Chip is used to generate a battery-backed-up Real-Time Clock.
4.1.2
Boot Mode/Boot Medium
The emCON-MX8MM Uboot can be booted either from the onboard eMMC, the NOR Flash, the SD-
Card interface or external via the USB Device interface. To switch between the options, the right
boot mode and boot device has to be configured via some Dip Switches.
The boot mode is configured via two processor pins which are available at the emCON connector.
A dip switch on the carrier board is used to configure the boot mode.
emCON Avari Baseboard (SW1):
SW1
SW2
SW3 SW[4:8]
Boot Mode
Configuration
ON
ON
X
X
Boot from Fuses
-
OFF
ON
X
X
Serial Downloader
USB
ON
OFF
X
X
Internal Boot
eMMC/SDC/NAND/NOR
OFF
OFF
X
X
Reserved
-
emCON Bvari Baseboard (SW4):
SW1
SW2
SW3
SW4
Boot Mode
Configuration
ON
ON
X
X
Boot from Fuses
-
OFF
ON
X
X
Serial Downloader
USB
ON
OFF
X
X
Internal Boot
eMMC/SDC/NAND/NOR
OFF
OFF
X
X
Reserved
-
