Receiver Card Interface Examples

The OEM7 receiver cards provide a number of 3.3V CMOS-level I/O pins for status indication and timing:

• COMx: CMOS-level UART ports

• Ethernet: 10/100 Ethernet port

• CAN1 and CAN2: CMOS-level CAN ports (external CAN transceivers required)

• PPS: Output pulse providing time reference signal (software configurable output rate, defaults to 1 Pulse Per Second)

• EVENTx_OUT: Variable Frequency output (a software-configurable clock output similar to PPS, off by default). (The EVENT1_OUT signal may also be referred to as an VARF.)

• PV: Position Valid (This signal drives high when the receiver has calculated a valid position)

• EVENTx_IN: Event inputs (with configurable polarity)

• USERIO: A user defined general purpose input or output (OEM729 only)

These I/O require additional ESD protection if they are to be routed to enclosure connectors. A protection circuit similar to the following examples must be used on any OEM7 CMOS-level signals that will be routed to an enclosure connector. The ferrite bead and small-value capacitor provide some immunity to electrostatic discharge events, but also serve to reduce radiated and conducted emissions from the enclosure.