CenterClick NTP200 Series Documentation - PPS Output
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Using the PPS Pins
Starting with Hardware version 15, the NTP200 and NTP250 support PPS output hardware function. All version of the NTP220 and NTP270 support PPS output and input.
Note that the pins are intended for short length cabling to other equipment that can accept a 5V signal. Long cables may suffer loss and reflections and the use of shielded cable is recommended.
Enabling PPS Output
By default, the PPS output pin is not enabled, to enable output run the 'pps output' command from the services menu.
When disabled, pins are driven to DC Ground. During bootup or reboot, the PPS output is disabled until the config is loaded.
The start of each second is at the rising edge, and the pulse width is 100msec.
Enabling PPS Input (NTP220/270 only)
By default, the PPS input pin is not enabled, to enable output run the 'pps input' command from the services menu.
When disabled, inputs are ignored. When enabled, a PPS source will be fed into the NTP algorithm identified as 'PSIN'.
The start of each second should be on the rising edge.
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 terminal block 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 (NTP200/NTP250 only) | Shared Ground |
| Ethernet | Isolated |
| Terminal Block | Shared Ground |
| PoE Input | Isolated |
| DC Input | Shared Ground, but note that most AC/DC adaptors provide isolation |
PPS Pinout - NTP200 and NTP250
| Pin Marking | Function |
|---|---|
| - | DC Ground |
| + | 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 appliance's driver cannot provide sufficent current to drive a coax cable with 50 Ohm termination.
PPS Pinout - NTP220 and NTP270
| Pin Marking | Function |
|---|---|
| O | PPS Output (when enabled) |
| G | DC Ground |
| I | PPS Input (when enabled) |
| A | Alarm Output (when enabled) |
The PPS and Alarm Output pins are 5V output pins with dedicated driver ICs that can push/pull up to 8mA of current. The appliance's driver cannot provide sufficent current to drive a coax cable with 50 Ohm termination.
The PPS Input pin is a wide-range input that can accept a positive range from 2.3V to 5.5V.
WARNING: The Alarm Output in is not a dry contact, it outputs 0V/5V and can source up to 8mA of current.
