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diff --git a/html/driver28.htm b/html/driver28.htm new file mode 100644 index 0000000..787ccb4 --- /dev/null +++ b/html/driver28.htm @@ -0,0 +1,133 @@ +<HTML> +<HEAD> + <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> + <META NAME="GENERATOR" CONTENT="Mozilla/4.01 [en] (Win95; I) [Netscape]"> + <TITLE>Shared memoy Driver +</TITLE> +</HEAD> +<BODY> + +<H3> +Shared Memory Driver</H3> + +<HR> +<H4> +Synopsis</H4> +Address: 127.127.28.<I>u</I> +<BR>Reference ID: <TT>SHM</TT> +<BR>Driver ID: <TT>SHM</TT> +<H4> +Description</H4> +This driver receives its reference clock info from a shared memory-segment. +The shared memory-segment is created with owner-only access for unit 0 +and 1, and world access for unit 2 and 3 +<H4> +Structure of shared memory-segment</H4> + +<PRE>struct shmTime { + int mode; /* 0 - if valid set + * use values, + * clear valid + * 1 - if valid set + * if count before and after read of + * values is equal, + * use values + * clear valid + */ + int count; + time_t clockTimeStampSec; /* external clock */ + int clockTimeStampUSec; /* external clock */ + time_t receiveTimeStampSec; /* internal clock, when external value was received */ + int receiveTimeStampUSec; /* internal clock, when external value was received */ + int leap; + int precision; + int nsamples; + int valid; + int dummy[10]; +};</PRE> + +<H4> +Operation mode=0</H4> +When the poll-method of the driver is called, the valid-flag of the shared +memory-segment is checked: + +<P>If set, the values in the record (clockTimeStampSec, clockTimeStampUSec, +receiveTimeStampSec, receiveTimeStampUSec, leap, precision) are passed +to ntp, and the valid-flag is cleared. + +<P>If not set, a timeout is reported to ntp, nothing else happend +<H4> +Operation mode=1</H4> +When the poll-method of the driver is called, the valid-flag of the shared +memory-segment is checked: + +<P>If set, the count-field of the record is remembered, and the values +in the record (clockTimeStampSec, clockTimeStampUSec, receiveTimeStampSec, +receiveTimeStampUSec, leap, precision) are read. Then, the remembered count +is compared to the count now in the record. If both are equal, the values +read from the record are passed to ntp. If they differ, another process +has modified the record while it was read out (was not able to produce +this case), and failure is reported to ntp. The valid flag is cleared. + +<P>If not set, a timeout is reported to ntp, nothing else happend +<H4> +Fudge Factors</H4> + +<DL> +<DT> +<TT>time1 <I>time</I></TT></DT> + +<DD> +Specifies the time offset calibration factor, in seconds and fraction, +with default 0.0.</DD> + +<DT> +<TT>time2 <I>time</I></TT></DT> + +<DD> +Not used by this driver.</DD> + +<DT> +<TT>stratum <I>number</I></TT></DT> + +<DD> +Specifies the driver stratum, in decimal from 0 to 15, with default 0.</DD> + +<DT> +<TT>refid <I>string</I></TT></DT> + +<DD> +Specifies the driver reference identifier, an ASCII string from one to +four characters, with default <TT>SHM</TT>.</DD> + +<DT> +<TT>flag1 0 | 1</TT></DT> + +<DD> +Not used by this driver.</DD> + +<DT> +<TT>flag2 0 | 1</TT></DT> + +<DD> +Not used by this driver.</DD> + +<DT> +<TT>flag3 0 | 1</TT></DT> + +<DD> +Not used by this driver.</DD> + +<DT> +<TT>flag4 0 | 1</TT></DT> + +<DD> +Not used by this driver.</DD> + + +<P>Additional Information + +<P><A HREF="refclock.htm">Reference Clock Drivers</A></DL> + +</BODY> +</HTML> |
