92 lines
2.4 KiB
Groff
92 lines
2.4 KiB
Groff
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.TH PHC2SYS 8 "November 2012" "linuxptp"
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.SH NAME
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phc2sys \- synchronize two clocks
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.SH SYNOPSIS
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.B phc2sys
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{
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.BI \-d " pps-device"
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[
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.BI \-s " phc-device"
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.BI \-i " interface"
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] |
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.BI \-s " phc-device"
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.BI \-i " interface"
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} [
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.BI \-c " phc-device"
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] [
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.BI \-P " kp"
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] [
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.BI \-I " ki"
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] [
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.BI \-R " update-rate"
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] [
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.BI \-N " clock-readings"
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]
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.SH DESCRIPTION
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.B phc2sys
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is a program which synchronizes two clocks in the system. Typically, it is used
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to synchronize the system clock to a PTP hardware clock (PHC), which itself is
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synchronized by the
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.BR ptp4l (8)
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program.
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Two synchronization modes are supported, one uses a pulse per second (PPS)
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signal provided by the source clock and the other mode reads time from the
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source clock directly. The PPS mode is usually preferred, because reading the
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PHC is slow and introduces an unknown error in the readings, but not all PHCs
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provide the PPS signal.
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.SH OPTIONS
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.TP
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.BI \-d " pps-device"
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Specify the PPS device of the master clock (e.g. /dev/pps0). With this option
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the PPS synchronization mode is used instead of the direct mode. As the PPS
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signal does not specify time and only marks start of a second, the slave clock
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should be already close to the correct time before
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.B phc2sys
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is started or the
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.B \-s
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option should be used too.
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.TP
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.BI \-s " phc-device"
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Specify the device of the master clock (e.g. /dev/ptp0). When this option is
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used together with the
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.B \-d
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option, the master clock is read only on start to fix an offset over 0.5
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seconds which cannot be fixed with PPS alone.
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.TP
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.BI \-i " interface"
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Similar to the
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.B \-s
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option, but specified by the interface which provides the master clock.
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.TP
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.BI \-c " phc-device"
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Specify the device of the slave clock (e.g. /dev/ptp1). The default slave clock
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is the system clock (CLOCK_REALTIME).
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.TP
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.BI \-P " kp"
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Specify the proportional constant of the PI controller. The default is 0.7.
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.TP
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.BI \-I " ki"
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Specify the integral constant of the PI controller. The default is 0.3.
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.TP
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.BI \-R " update-rate"
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Specify the slave clock update rate when running in the direct synchronization
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mode. The default is 1 per second.
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.TP
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.BI \-N " phc-num"
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Specify the number of master clock readings per one slave clock update. Only
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the fastest reading is used to update the slave clock, this is useful to
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minimize the error caused by random delays in scheduling and bus utilization.
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The default is 5.
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.TP
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.BI \-h
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Display a help message.
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.SH SEE ALSO
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.BR ptp4l (8)
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