Reference Clock Drivers

Last update: May 4, 2022 17:05 UTC (dbea9b7d4)

Reference Clock Drivers

Support for most of the commonly available radio and modem clocks is included in the default configuration of the NTP daemon for Unix xntpd. Individual clocks can be activated by configuration file commands, specifically the server and fudge commands described in the xntpd program manual page. The following discussion presents Information on how to select and configure the device drivers in a running Unix system.

Radio and modem clocks by convention have addresses in the form 127.127.t.u, where t is the clock type and u is a unit number in the range 0-3 used to distinguish multiple instances of clocks of the same type. Most of these clocks require support in the form of a serial port or special bus peripheral. The particular device is normally specified by adding a soft link /dev/device_u to the particular hardware device involved, where u correspond to the unit number above.

Following is a list showing the type and title of each driver currently implemented. The compile-time identifier for each is shown in parentheses. Click on a selected type for specific description and configuration documentation, including the clock address, reference ID, driver ID, serial port device name and speed, and features (line disciplines, etc.). For those drivers without specific documentation, please contact the author listed in the Copyright Notice page.

* All TrueTime receivers are now supported by one driver, type 5. Types 15 and 25 will be retained only for a limited time and may be reassigned in future.