Alternate Functions - Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual

Reference Manual
GPIO - General Purpose Input/Output

32.3.4 Alternate Functions

Alternate functions are connections to pins from peripherals, i.e. Timers, USARTs, etc.. These peripherals contain route registers,
where the pin connections are enabled. In addition, the route registers contain a location bit field that configures which pin an output of
that peripheral will be connected to if enabled. After connecting a peripheral, the pin configuration stays as set in GPIO_Px_MODEL,
GPIO_Px_MODEH and GPIO_Px_DOUT registers. For example, the pin configuration must be set to output enable in GPIO_Px_MOD-
EL or GPIO_Px_MODEH for a peripheral to be able to use the pin as an output.
It is not recommended to select two or more peripherals as output on the same pin. The reader is referred to the pin map section of the
device data sheet for more information on the possible locations of each alternate function.
32.3.4.1 Analog Connections
When using the GPIO pin for analog functionality, it is recommended to disable the over voltage tolerance by setting the corresponding
pin in the GPIO_Px_OVTDIS register and setting the MODEn in GPIO_Px_MODEL or GPIO_Px_MODEH equal to DISABLE to disable
the input sense, output driver and pull resistors.
32.3.4.2 Debug Connections
32.3.4.2.1 Serial Wire Debug Connection
The SW Debug Port is routed as an alternate function and the SWDIO and SWCLK pin connections are enabled by default with internal
pull up and pull down resistors, respectively. It is possible to disable these pin connections (and disable the pull resistors) by setting the
SWDIOTMSPEN and SWCLKTCKPEN bits in GPIO_ROUTEPEN to 0.
The Serial Wire Viewer pin, SWV, can be enabled by setting the SWVPEN bit in GPIO_ROUTEPEN. This bit can also be routed to
alternate locations by configuring the SWVLOC bitfield in GPIO_ROUTELOC0.
32.3.4.2.2 JTAG Debug Connection
The JTAG Debug Port is routed as an alternate function and the TMS, TCK, TDO, and TDI pin connections are enabled by default with
internal pull up, pull down, no pull, and pull up resistors, respectively. It is possible to disable these pin connections (and disable the pull
resistors) by setting the SWDIOTMSPEN, SWCLKTCKPEN, TDOPEN, and TDIPEN bits in GPIO_ROUTEPEN to 0.
32.3.4.2.3 Disabling Debug Connections
When the debug pins are disabled, the device can no longer be accessed by a debugger. A reset will set the debug pins back to their
enabled default state. The GPIO_ROUTEPEN register can only be updated when the debugger is disconnected from the system. Any
attempts to modify GPIO_ROUTEPEN when the debugger is connected will not occur. If you do disable the debug pins, make sure you
have at least a 3 second timeout at the start of your program code before you disable the debug pins. This way the debugger will have
time to connect to the the device after a reset and before the pins are disabled.
32.3.5 Interrupt Generation
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