23
24
ER
- blinks ON/OFF after a 511/511E test has timed
out. See Section 5.2.3 (Test Pattern Generator) for
more information.
- flashes once to indicate that a CRC error has
occurred (during normal operation) or bit errors
have occurred (during 511/511E test).
- Only at power up, blinks once every 200 ms if
the DTE Rate is set to an unsupported setting.
TM
glows yellow to indicate that the Model 1094ARC
has been placed in Test Mode. The unit can be
placed in test mode by the local user or by the
remote user. The TM LED will flash for 400msec
when a valid packet is received from the Model
1001MC.
NS
(No Signal) glows red to indicate that the local
Model 1094ARC is not connected with the remote
Model 1094ARC.
5.2 TEST MODES
The Model 1094ARC offers two proprietary loopback test modes,
plus a built-in V.52 BER test pattern generator to evaluate the condition
of the modems and the communication link. These tests can be acti-
vated physically from the front panel or via the interface.
5.2.1 Overview
Figure 12 below shows the major elements used in the loop-back
and pattern tests available in the Model 1094ARC. Each block has
several functions. Following Figure 12 are descriptions that show how
the elements are used during Test Modes.
Figure 12: Block Diagram Model 1094ARC
Framer
The framer is used to determine the status of
the line. In normal operation the framer transmits
and expects to receive framed packets from the
far end. If the framer receives framed packets
from the far end, CTS and CD will be active. If
framed packets are not received, CTS and CD
will be inactive. The restart procedure uses this
information to determine if a valid connection is
made (cable disconnect, poor cable quality, etc).
In normal Data Mode, if the box receives 4 sec-
onds of unframed packets it will restart the box
and begin trying to re-establish a connection
with the far end. The distinction between framed
packets and unframed packets becomes impor-
tant when we discuss the Pattern Generator.
Pattern Gen/Det
This part of the Processor generates and
detects the 511/511E patterns. When transmit-
ting 511 patterns, the information is unframed
(because it originates after the framer) and is
intended to be evaluated only by another
Processor. If the units are in Data Mode 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, we force the pattern
generator to time out before it can cause the link
to be killed.
Loop Control
This part of the Processor is used to control
loop-backs. In a Local Loop, the data is looped
back towards the local DTE. In a Remote Loop,
the data is looped back to the line, but it is also
allowed to pass through to the framer and to the
remote DTE.
Pattern
Gen/Det
Loop
Control
Loop
Control
Pattern
Gen/Det
Processor
Processor
Framer
Framer
Line
