Ixia IRIG-B Auxiliary Function Device (AFD2)
15-2
Ixia Platform Reference Manual Manual, Release 6.30
15
Figure 15-2. AFD2 in a Chassis Chain
The IxExplorer GUI displays the status of the IRIG-B interface to the user.
shows the Chassis Properties dialog with status information. The
connection is determined to be either
locked
or
unlocked
. In the Locked state, the
chassis is locked to IRIG-B time within 150nS. In the unlocked state, the AFD2
IRIG-B hardware operates to lock its VCXO to 1PPS pulse.
The process of generating the Lock status for the AFD2 consists of getting IRIG-
B time lock and then synchronizing the internal clock to the IRIG-B 1PPS pulse.
The AFD2 does not enter the ‘Lock’ state until the VCXO lock condition is met.
In the unlocked state, the chassis in the unlocked chain are not accurately time-
synchronized to the rest of the chain.
In operation, once a chassis chain is constructed and the chassis are
synchronized, you can clear the timestamps to provide a baseline time for all
chassis in the chain. The chain operations are then locked until such time that the
IRIG-B lock is lost by a member of the chain. Data sent from one port in the
chain to another provides one-way latency measurements by subtraction of the
transmit time stamp from the receive time stamp.
For large or very remote chassis chains, the chassis chain properties provide an
offset delay. This delay is defaulted to 5 seconds. For chassis chains where the
communication delays are significant, as in worldwide or large chains, a longer
delay should be selected to allow for setup communication delays. The delay is
the time of a particular chassis operation (for example, start transmit, stop
transmit) plus the configured delay for any synchronous operation. When an
operation for the entire chain is executed, this delay is added to the operation. A
dialog opens indicating that the operation is in process when the delays are
significant.
The chassis time is taken from any chassis with a IRIG-B interface attached. The
setup for the chassis chain requires that all chassis in the chain be locked. This is
indicated in the IxExplorer GUI.
The critical operation for a virtual chain is the reset of the System Time Stamps.
All other actions are dependent on the synchronous execution of this operation.
Caution:
A chassis connected to an AFD2 chassis does not operate properly if
set to Synchronous time source, unless the sync cable is disconnected.
Sync
Out
Sync
In
Sync
In
Ixia XM2
(slave)
Ixia XM2
(slave)
Ixia AFD2 IRIG-B
Receiver (master)
Sync
Out
USB cable
provides power and COM3 channel
Customer’s IRIG
Receiver