User's Manual

System Overview and Functional Block Descriptions
1322x Sensor Node Reference Manual, Rev. 1.1
Freescale Semiconductor 3-7
— The onboard speaker is automatically disconnected if a headset is plugged-in.
3.10 GPIO Connector
The GPIO connector (J2) provides a number of data interfaces and GPIO for external system expansion,
Section 4.8, “GPIO Connector” gives details.
• Some of the GPIO are shared with onboard devices. The user should take care to avoid conflict.
• Power supply voltage is provided
— Current draw should be limited to 50 mA.
— A separate regulated voltage can be enabled
• Provision is made to supply an external reference clock if desired.
3.11 Clocks
The MC1322x Sensor Mode provides for two system clock sources.
• MC1322x Reference Oscillator - The default frequency for the reference oscillator is 24 MHz and
the mounted crystal X1 is a 24 MHz device that meets MC1322x specifications. There are two
additional options for the module
— X1 can be replaced by a 13-26 MHz crystal (it must meet MC1322x specifications), however,
the onboard PLL must be used in this case. The pcb provides for PLL filter components, but
these are not populated.
— An external clock source can be supplied as the reference source (typically 24 MHz). The
frequency must be accurate to +/-40ppm. The external clock source is supplied through GPIO
Connector J2, and crystal X1 must be removed and capacitor C58 mounted (see Chapter 5,
“Schematic, Board Layout, and Bill of Material”, Sheet 1).
— 32.768 kHz Crystal Oscillator - Provision is also made for an optional secondary 32.768 kHz
crystal X2. This oscillator can be used for a low power accurate timebase. The module comes
without this crystal and its load capacitors C7 and C12 unmounted (see Chapter 5, “Schematic,
Board Layout, and Bill of Material”, Sheet 1).