CenterClick NTP200 and NTP250 Documentation - PPS Output

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Using the PPS Output Pins

Starting with Hardware version 15, the NTP200 and NTP250 support a PPS output hardware function.

Enabling Output

By default, the PPS output pins are not enabled, to enable output run the 'pps output' command from the services menu.

When disabled, both pins will be driven to DC Ground. During bootup or reboot, the PPS output is disabled until the config is loaded.

Connecting Devices

The pluggable terminal block connector can accept wire of 26 to 20 AWG and requires a precision screwdriver such as a 1.5mm tip width flathead.

Electrical Isolation

WARNING: The PPS output pins are not electrically isolated from several other ports on the appliance. Connecting devices with different ground potentials or that could cause ground loops can damage the appliance.

Connector	Isolated from PPS Output
GPS Antenna	Shared Ground
USB uB Console	Shared Ground
USB A	Shared Ground
Ethernet	Isolated
PPS Output	Shared Ground
PoE Input	Isolated
DC Input	Shared Ground, but note that most AC/DC adaptors provide isolation

PPS Pinout

Pin Marking	Function
-	DC Ground
+	0V/5V PPS Output (when enabled)

The PPS Output pin (marked +), is a 5V output pin with a dedicated driver IC that can push/pull up to 8mA of current. The start of each second is at the rising edge, and the pulse width is 100msec.

Note that the output pins are intended for short length cabling to other equipment that can accept a 5V input. Long cables may suffer loss and reflections. The appliance's driver cannot provide sufficent current to drive a coax cable with 50 Ohm termination.