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Appendix C ‑ Clock Set Sequence
I ntroduction
The GCS can be used to synchronize the real-time clocks of various rail signal products.
The procedure for doing so is referred to as the Clock Set Sequence. The sequence
utilizes several different schemes that are categorized into three groups. The groups are
identified by the hardware and messaging interfaces they employ. They are referred to
as ASCII Messaging, Peer Protocol and SNTP. Each is described in the sections that follow.
Although the GCS employs three very different Clock Set Sequences, they operate on
a non-interfering basis. SNTP can be active concurrently with either ASCII Messaging or
Peer Protocol.
ASCII M essaging
via
RS‑232
The ASCII Messaging scheme utilizes an RS‑232 connection between the Device Port of
the GCS and the Target Device. It is used with all non-Microlok II Target Devices. ASCII
messages with appropriate formatting and syntax are transmitted by the GCS and then
validated and accepted by the Target Device. Irrespective of the assigned Recorder
Type (i.e., Target Device) the following properties apply to the Clock Set Sequence.
Automatically Initiated – The sequence will be automatically initiated as defined by
the Clock Set Interval setting (once every 1, 12 or 24 hours). Refer to the section entitled
“Clock Set Interval (optional)” on page 19 for additional details.
Five-Minute Mark – The sequence commences on the five-minute mark after the start
of the hour (e.g., 14:05:00). Some Target Devices (not MICRO‑AIDE designed) are not
prepared to execute a machine driven clock set command on the hour mark. The fiveminute delay avoids this problem.
Manual Initiation – The sequence can also be manually initiated at any time and without
delay by executing the Go command. Refer to the section entitled “Updating the Target
Device Clocks” on page 19 for additional details.
DP Sequence – Whether automatically or manually initiated, the sequence starts with
Device Port T/DP1 (if assigned a Target Device, otherwise DP2) and proceeds through
DP6 (DP2 for the GCS‑2). Device Ports with a Recorder Type setting of None are by‑
passed.
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