transmitting data and the pattern generator is
enabled on one end of the link, the far end will
begin receiving unframed packets and assume
that the line has gone down. During test modes,
the pattern generator is forced to time out before
it can cause the DSL link to go down.
Loop Control
This part of the Processor is used to control
Remote Loopback test mode. In a Remote
Loop, the 511/511/Edata is looped back to the
line and to the remote unit over the DSL span.
Restart Procedure
The restart procedure is in place to allow the
and Time Outs
units to re-establish a connection after the
framer begins seeing unframed packets. The
Test Mode Timing Chart below shows the
amount of time the framer must see consecutive
unframed packets before the unit will restart and
try to establish a new line connection. The rea-
son that there are different Restart Times will
become apparent after reading the rest of the
document. The 511/511E Time Out shown refers
to the amount of time the 511/511E pattern will
be valid. At the end of this time the pattern will
automatically turn itself off and the normal data
path will be re-established. The ER led will flash
indicating to the user that the test has timed out.
The ER led will stop flashing once the 511/511E
switch is placed into the normal position.
Symbol Indicators
This symbol designates the origination or the
termination of a data path. The direction of the
arrow connected distinguish the two data paths.
This symbol designates an invalid data path. If
there is data present it should be ignored.
19
6.4.2 Loops and Patterns
The following section describes the Remote Loopback/BER test
modes.
Remote Digital
When Remote Loop/511 or Remote Loop/511/E
is enabled via the front panel switch, the
Remote unit’s Restart Timer is set to one
minute. This is because when the 511/511E gen-
erator is initiated on the local unit, the Remote
framer begins seeing unframed packets. The
Remote unit can not distinguish the 511/511E
pattern from the line being disconnected, so the
Restart Timer has been lengthened to allow the
pattern generator to function. Once the 511/511E
test is started, the Local unit changes its' Restart
Timer to one minute. The pattern originates with-
in the Processor and is sent to the Remote unit.
It is then looped back to the Local unit where it
is evaluated for errors. After 45 seconds, the
Pattern Generator will timeout and stops send-
ing the pattern. The ER led will begin blinking
until the user turns off the 511/511E switch.
6.4.3 Using the V.52 (BER) Test Pattern Generator
To use the V.52 BER tests in conjunction with the Remote Digital
Loopback tests, follow these instructions:
1.
Locate the Remote Loop/511 & Remote Loop/511E toggle
switch on the front panel of the 1088 and move it DOWN.
This activates the Remote Loop with V.52 BER and transmits
a “511” test pattern into the loop. If any errors are present,
the local unit’s red “ER” LED will blink sporadically.
20
Test Mode Timing
Item
Elapsed Time (seconds)
Start Up
50
Data Mode
4
511/511E Generator Enabled 60 (The generator will stop after 45 seconds.)
Remote End of an RDL
60
511/511E Time Out
45 (The pattern generator will automatically turn
off after 45 seconds. The ER LED will flash until
the user turns off the 511/511E switch.)
Pattern
Gen/Det
Loop
Contr
ol
Loop
Contro
l
Pattern
Gen/Det
Processor
Processor
Framer
Framer
Line