Download gcs-2 gcs-6 clock synchronizers - MICRO-AIDE

GCS U ser M anual
Duration – The GCS always attempts to set the time and date for each assigned Target
Device. Typically, 15 to 20 seconds are required to set the time and date for each Target
Device.
Latency Compensation – The Terminal Ports implemented on all MICRO‑AIDE CWR, VDL
and PSM products are designed to support high speed, machine-driven interfaces (e.g.,
a PC running GEA software). Each is prepared to accept and execute time and date
commands immediately. Furthermore, as each character that comprises the command
string is received, it is acted upon by the device. No echo character check is required
by the GCS. Consequently, no delays are introduced between characters and the entire
command can be sent in 9 msec (35 characters, 10 bps at 38,400 Baud).
This is not the case with the HCA, EC‑4 (216DL module) and HXP‑3. The HCA and EC‑4
serial interfaces require that each character sent be checked against an echoed char‑
acter. This introduces delays as the GCS must wait to receive the echoed character. The
HXP‑3 does not echo characters. To assure good performance with the HXP‑3, the GCS
imposes a .5 second delay between each character that it sends. From start to finish, the
time set command for these three products will take several seconds to send. The GCS is
designed to compensate for this characteristic, which would otherwise result in an unac‑
ceptable time discrepancy.
The time set command is always preformulated with a clock setting that is several sec‑
onds ahead of the current GCS time. By way of example, suppose the worst-case delays
in total will take the time set command 8 seconds to be sent. The command will include
a clock setting that is advanced by 10 seconds. After the command is entirely sent, the
GCS will wait until 10 seconds have precisely expired. The carriage return character is
then sent and the Target Device clock is updated. The GCS and Target Device clocks will
differ by a very small amount related to the execution time of the Target Device.
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GPS Signal Loss – The sequence will be initiated and completed irrespective of the GPS
signal status. This applies even if the Alarm Output is active indicating a loss of GPS signal
for seven or more days. The internal real-time clock used by the GCS has an accuracy
specification of ±.26 seconds per day. Even without GPS-based synchronization, the GCS
clock will be significantly more accurate than the real-time clock used by any Target
Device other than a MICRO‑AIDE CWR‑24E, CWR‑72E, CWR‑264XL or VDL. The latter use
the same real-time clock chip with an accuracy rating of ±3 ppm.
Log Entries – The success or failure of each clock set attempt (automatic or manual) is
noted by an entry in the Log.
Alarm Activation – Three consecutive failures to set the clock at any given Target Device
will activate the Alarm Output. Failures can be the result of either an automatically or
manually initiated sequence.
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