SMP Gateway User Manual • 201
Also, the SMP Gateway does not perform accurate time-tagging when I/O changes are received
from a device, because the transmission delay is unpredictable. For the time tag to be accurate, the
device must time-tag the I/O changes itself.
The following sections present the various time distribution features of the SMP Gateway.
21.4.1 Configuring IRIG-B Time Distribution
IRIG-B time distribution is the ability, for an SMP Gateway, to distribute time adjustment
information to various devices using IRIG-B signals.
Unlike using SNTP or a master protocol’s time adjustment feature, IRIG-B time distribution
requires the SMP Gateway to be time-adjusted by a reliable source such as an IRIG-B signal or by
GPS.
Setting up IRIG-B is described in the installation guide of your SMP Gateway, which is included
on the SMP Gateway Software & Tools CD-ROM.
Some additional configuration may be required, using SMP Config.
If the SMP Gateway is time-adjusted using GPS:
Under the System branch, select Time. If the Time instance has not been created yet, type a
name in the blank Name text box, and then click again the Time branch.
Under the Time instance branch, select the General branch.
Under GPS IRIG-B Distribution, select the IRIG-B format to which you want the GPS time
information to be converted.
Note : If the SMP Gateway is time-adjusted by an IRIG-B signal, the distributed IRIG-B
signal will use the same IRIG-B format. For example, if the SMP Gateway’s input
is an IEEE 1344 signal, the output will also be a IEEE 1344 signal.
If the SMP Gateway is part of a redundancy group, and you want it distribute time even while on
standby:
Under the System branch, select Time. If the Time instance has not been created yet, type a
name in the blank Name text box, and then click again the Time branch.
Under the Time instance branch, select the General branch.
Select the Distribute IRIG-B Signal checkbox.
21.4.2 Setting Up the SMP Gateway to Act as an SNTP Server
If some devices can be configured as SNTP clients, the SMP Gateway can itself be configured to
act as an SNTP server for these devices.
To configure the devices as SNTP clients, refer to each device’s user manual.
To set up the SMP Gateway as an SNTP server, proceed as follows:
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