Figure 12. Block Diagram Local Loop Mode 1
Figure 13. Block Diagram Local Loop Mode 2
Local Loop
When the unit is placed into a Mode 1. Local
with 511/511E
Loop and the 511/511E pattern generator is acti-
vated, the local pattern generator begins send-
ing out a 511/511E pattern to the Loop Control
block. The Loop Control block will loop this data
back to the 511/511E pattern detector block,
which will evaluate the data for errors. Because
the 511/511E pattern generator is contained
within the Processor the data is unframed so the
framer will begin seeing unframed packets. The
framer receives this unframed data and can not
distinguish this information from a line discon-
nection (this would cause the units' Restart pro-
cedure to start). What we have done to allow
this mode to work is to add time outs for the pat-
tern generators. When the 511/511E is initiated,
the line restart procedure is changed to one
minute. The 511/511E pattern will timeout after
45 seconds. So if the 511/511E is turned on dur-
ing a local loop, the restart procedure is set to
one minute, but the 511/511E pattern will time
out after 45 seconds, allowing the framer to
begin seeing framed packets (and not restart
the box).
23
Local Loop
After the 511/511E pattern times out, the ER led
with 511/511E
will begin flashing. It will remain this way until
(continued)
the pattern generator switch is turned off. Note
that the data at the local DTE and the remote
DTE are not valid. Because the data is
unframed there is no way for the framer to send
this data out to the DTE. This is an important
distinction because other Patton units will send
out the 511 pattern.
When the unit is placed into a Mode 2 Local
Loop, the 511/511E pattern generator on the
local unit is unavailable for transmission. Figure
15 displays the 511/511E pattern generator,
showing that data path connections are not
available. The 511/511E pattern generator is still
available on the remote unit. For more informa-
tion on the proper operation of this pattern gen-
erator please refer to the "Remote Digital Loop
with 511/511E" section.
24
Pattern
Gen/Det
Loop
Contr
ol
Loop
Contro
l
Pattern
Gen/Det
Processor
Processor
Framer
Framer
Line
Pattern
Gen/Det
Loop
Contr
ol
Loop
Contro
l
Pattern
Gen/Det
Processor
Processor
Framer
Framer
Line
Pattern
Gen/Det
Loop
Contr
ol
Loop
Contro
l
Pattern
Gen/Det
Processor
Processor
Framer
Framer
Line
Pattern
Gen/Det
Loop Contr
ol
Loop Contro
l
Pattern
Gen/Det
Processor
Processor
Framer
Framer
Line
Figure 14. Block Diagram Local Loop Mode 1 with 511/511E
Figure 15. Block Diagram Local Loop Mode 2 with 511/511E
