Pin Descriptions
5-8 Revision 10
Special Function Pins
Name Type Polarity/Bus Size Description
NC No connect
This pin is not connected to circuitry within the device. These pins can
be driven to any voltage or can be left floating with no effect on the
operation of the device.
DC Do not connect.
This pin should not be connected to any signals on the PCB. These
pins should be left unconnected.
LPXIN In 1 Low power 32 KHz crystal oscillator.
Input from the 32 KHz oscillator. Pin for connecting a low power 32
KHz watch crystal. If not used, the LPXIN pin can be left floating. For
more information, see the PLLs, Clock Conditioning Circuitry, and On-
Chip Crystal Oscillators section in the SmartFusion Microcontroller
Subsystem User’s Guide.
LPXOUT In 1 Low power 32 KHz crystal oscillator.
Output to the 32 KHz oscillator. Pin for connecting a low power 32 KHz
watch crystal. If not used, the LPXOUT pin can be left floating. For
more information, see the PLLs, Clock Conditioning Circuitry, and On-
Chip Crystal Oscillators section in the SmartFusion Microcontroller
Subsystem User’s Guide.
MAINXIN In 1 Main crystal oscillator circuit.
Input to the crystal oscillator circuit. Pin for connecting an external
crystal, ceramic resonator, or RC network. When using an external
crystal or ceramic oscillator, external capacitors are also
recommended. Refer to documentation from the crystal oscillator
manufacturer for proper capacitor value.
If an external RC network or clock input is used, the RC components
are connected to the MAINXIN pin, with MAINXOUT left floating. When
the main crystal oscillator is not being used, MAINXIN and MAINXOUT
pins can be left floating.
For more information, see the PLLs, Clock Conditioning Circuitry, and
On-Chip Crystal Oscillators section in the SmartFusion Microcontroller
Subsystem User’s Guide.
MAINXOUT Out 1 Main crystal oscillator circuit.
Output from the crystal oscillator circuit. Pin for connecting external
crystal or ceramic resonator. When using an external crystal or ceramic
oscillator, external capacitors are also recommended. Refer to
documentation from the crystal oscillator manufacturer for proper
capacitor value.
If an external RC network or clock input is used, the RC components
are connected to the MAINXIN pin, with MAINXOUT left floating. When
the main crystal oscillator is not being used, MAINXIN and MAINXOUT
pins can be left floating.
For more information, see the PLLs, Clock Conditioning Circuitry, and
On-Chip Crystal Oscillators section in the SmartFusion Microcontroller
Subsystem User’s Guide.
