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HIGH-SPEED 2-WIRE SHORT-RANGE DSL LINE DRIVER RACK CARD
• 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 four seconds 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 important
when we discuss the pattern generator.
• Pattern Gen./Det.: This part of the processor generates and detects the
511/511E patterns. When transmitting 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 loopbacks. 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.
5.2.2 R
ESTART
P
ROCEDURE AND
T
IMEOUTS
The restart procedure is in place to allow the units to re-establish a connection
after the framer begins seeing unframed packets. The Test Mode timing chart on
the next page 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 reason that there are different Restart Times will become
apparent after reading the rest of the document. The 511/511E timeout 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.
