5.3.2 Loops and Patterns

The following section describes the Test Modes used in the Model 1094A. At the bottom of each Test Mode, a figure is included to show the data path.

Local Loop

There are two different modes of operation for a

Framer

Pattern

Loop

 

Gen/Det

Control

 

Processor

Line

Loop Pattern

Control Gen/Det

Processor

Framer

Local Loop depending on the status of the units

at the time that the Local Loop is initiated. If the

Figure 7. Block Diagram Local Loop Mode 1

units are not in linked (NS LED on) and the

Local Loop is initiated, either by the front panel

switch or the DTE interface, the unit will enter

mode 1. If the units are linked, NS LED off, then

the unit will enter a mode 2 Local Loop.

A Mode 1 Local Loop is shown in Figure 7.

When the Local Loop is initiated, either by the

Framer

Pattern

Loop Control

Line

Loop Control

Pattern

Framer

Gen/Det

 

Gen/Det

 

 

 

 

 

Processor

 

Processor

 

 

front panel switch or the DTE interface, the loop

will be activated within the local Processor. The

data present at the local DTE interface will be

looped back to the local DTE by the Loop

Control block within the Processor. Any data

present on the line or at the far end DTE inter-

face is invalid. The remote unit will remain in the

StartUP mode, NS LED on, CTS LED yellow,

and CD LED yellow, until the local unit is taken

out of the Local Loop mode. After the Local

Loop is deselected, the units will both be in

StartUP mode and the link will be established.

A mode 2 Local Loop is shown in Figure 8.

When the Local Loop is initiated, either by the

front panel switch or the DTE interface, two sep-

arate loop paths will be started. In the first path,

data presented to the local DTE interface will be

looped back to the local DTE within the framer.

In the second path, data presented at the far

end DTE will be transmitted to the local DTE

and then looped back within the local DTE Loop

Control block with the Processor. After the Local

Loop is deselected, the units will be placed back

into DataMode and the normal data paths will be

re-established.

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Figure 8. 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).

 

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Patton electronic 1094A Loops and Patterns, Local Loop There are two different modes of operation for a, With 511/511E