Specifications

2-14
Reference Guide
Model No.
Running Head
Data Modules and Applications Applications
Each OCU-DP port can be independently programmed to operate at 2.4, 4.8, 9.6, 19.2, and 56
Kbps in either DSO-A, (one channel per DS0) or DS0-B format, which allows multiple data
ports from multiple OCU-DP cards in the system to be mapped into the same DS0 time slot.
If the DS0-B format is selected, then the user specifies the type of DS0-B format required (b-5,
b-10 or b-20) and the sub-rate position that the data port occupied by the data port within the
DS0-B frame.
In switched-56K mode, an OCU-DP port provides a connection for an external Switched-56K
DSU/CSU that will perform all call set-up and dialing functions. The OCU-DP card converts
the call set-up commands into standard signaling and sends the signaling over the WAN
facility.
All OCU-DP cards support a low speed secondary channel that is established in the 8
th
bit
position of the DS0 time slot to which the OCU-DP port is assigned. The secondary channel
can be used for testing and maintenance of the main circuit or for the transmission of other,
independent, low speed data. The specification table shows the secondary channel rates
associated with the standard primary port rates of the OCU-DP card.
The 8249 OCU-DP card also supports two methods of error correction. The first is known as
“Majority Vote” and applies to the lower data rates, specifically, 2.4, 4.8 and 9.6 Kbps. The
other is known as the BCH (Bose-Chaudhuri-Hocquenghem) method and applies to data rates
of 19.2 Kbps and 56 Kbps. In the case of a 19.2 Kbps circuit, the error correction information
is placed in the same DS0 that the circuit occupies. In the case of a 56 Kbps circuit, the error
correction information is placed in a following, adjacent DS0 time slot on the WAN aggregate.
On all OCU-DP cards’ performance statistics is collected by the system and are available
through the user interface. Performance statistics include Errored Seconds (any second with
an error), Severely Errored Seconds (any second with an error rate exceeding 10E-3) and
Consecutive Severely Errored Seconds (CSES). They are displayed in hour intervals for up to
24 hours. CSES are counted by the system once ten consecutive Severely Errored Seconds are
logged. The CSES counter stops if the system logs ten consecutive non-Severely Errored
Seconds.
An OCU-DP port on the 8249 card may be programmed for OCU mode or CSU mode. OCU
mode is the most common and is used whenever the OCU-DP port attaches to a CSU/DSU
over a four-wire circuit. CSU mode allows the card to be connected directly to the digital
network.
Software initiated diagnostics supported by the OCU-DP card include the setting of six
different loop backs. Three of these act on the OCU-DP card itself and are known as local loop
backs and the other three generate loop back patterns to remote devices and are known as
remote loop backs. Among local loop backs, there are three types:
•
loop backs of the 4-wire analog interface of the OCU-DP port towards the attached CSU
•
loop backs of the 4-wire OCU-DP interface towards the network
•
loop backs towards the network at the point where the OCU-DP card interfaces with the
system bus