Verilink 1558D (34-00255) Product Manual - Manual (Page 39)

LAPS Operation 4-13 1558D APS CSU/DSU
seconds or more, after which, the NET device should be
unlooped.
NPC Payload Loop
The NPC Payload loopback is used to loop a far end slave
unit that is configured to operate in the transparent mode
(CSU Disabled option). In this mode the far end slave card
will not respond to any ESF CSU commands. Normally, this
application is used only by an IXC internal network protec-
tion applications. Note that a NPC Payload loop is function-
ally the same type as a Far Payload loopback.
A NPC Payload loopback is used to loop the slave 1558D
unit from the master unit. At the far end slave unit, the NPC
Payload loopback loops the incoming T1 signal (RX) com-
ing from the network (NET A or NET B) port and loops this
signal back to the network (TX). Both the signal and CRC is
regenerated. In addition to looping the signal back to the
network, the signal is also transmitted to the DTE port.
To initiate a NPC Payload loop, first target the path (A or B)
that you want to test by moving the cursor highlight to the
Target: field and then, using the spacebar, toggle the field
until it displays the side that you want to loop (Side A or
Side B). After you have selected either the A or B side as
the target for testing, move the cursor highlight to the Loop
field and toggle the field, using the space bar, until the field
displays NPC Payload. Then momentarily depress the
<enter> key. The LAPS will respond by sending the appro-
priate loop command to the far slave unit. After a few
moments, notice that the FAR status field has changed from
Soft Inhibit or StandBy to PL LP. Also note that the far end
1558D front panel Loop LED indicator is on.
To unloop the unit, simply move the cursor highlight to the
Unloop field and toggle the field, using the space bar, until
NPC Payload is displayed. Then depress the <enter> key.
The LAPS will issue an unloop command. After a few
moments note that the FAR status field changes from PL LP
to Soft Inhibit or StandBy. Also note that the Loop LED
indicator on the far slave 1558D turns off. The NPC Payload
loop is now off.
BERT Testing
The user can perform BERT testing from a Master unit by
accessing the Maintenance screen. In the lower right hand
and left hand portions of the display are the command/tog-
gle/information fields that are used for BERT testing. These
fields and their use are discussed below.
Pattern: Specifies which pattern will be transmitted during
test. When the 3 or 5-bit, user-defined pattern is chosen, the
user may type in any pattern of 1s and/ or 0s to be transmit-
ted. Pressing <enter> with the cursor positioned on this field
will cause the pattern to be transmitted for the period of time
specified in ‘Test Time’. The choices are: QRSS, 1:8, 3:24,
all Ones, all Zeros, user definable 3-bit, and user definable
5-bit.
If the 1558D DTE is configured for AMI opera-
tion, the test sets must be set to generate either a
511, 2047, or 1:7 pattern. If the 1558D is config-
ured for B8ZS operation, any pattern may be
used (511, 2047, 1:7, QRSS, 3:24, etc.). When
sending a 1:7 pattern, though, some T1 test sets
inherently cause generation of a yellow alarm
condition.
Test Time: Defines the run-time of test pattern generation
and error accumulation and starts the test. Pressing <enter>
with the cursor positioned on this field will cause the
selected pattern to be transmitted for the specified period of
time. If the Maintenance menu is exited, pattern testing is
halted. The choices are: 15 Minutes, 30 Minutes, 45 Min-
utes, 1 Hour, and Continuous.
Runtime: Shows the amount of time elapsed since a timed
Pattern test began. Note that this field only appears on the
screen when a test is running.
Near CRC Errors: A display-only field for viewing the
number of CRC errors which are received at the Near Target
receive path.
Far CRC Errors: A display-only field for viewing the
number of CRC errors which are received at the Far Target
receive.Far CRC Errors are only reported if the 1558D is
configured as a Master. Slave 1558D units do not report Far
CRC Errors.
Reset Errors: Pressing <enter> with the cursor positioned
on this field causes both the Near and Far CRC accumula-
tors to be cleared (only if Master 1558D).
It is important to understand that the 1558D does not allow
testing (loop or BERT) on the active path. To perform test-
ing on a given path the user must first configure the path to
the StandBy mode, Soft Inhibit mode or Manual Inhibit
mode. Once the path to be tested is in one of these modes,
the LAPS will allow the user to perform testing.
BERT testing can be performed either to loopbacks or
straight away to the far end. To perform a BERT test, the
user should follow the steps discussed below.
1. Select the path to be tested using the TARGET toggle
field.
2. Move the cursor highlight to the Pattern field and then,
using the spacebar, toggle the field until the desired user
pattern is display. The available patterns are; QRSS, 1:8,
3:24, all Ones, all Zeros, user definable 3-bit, and
user definable 5-bit.
3. Next, move the cursor highlight to the Test Time field
and then, using the spacebar, toggle the field to the