XRT72L13 Datasheet, PDF (274/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
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PRELIMINARY
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
"Transmit Overhead Data Input Interface" (using
Method 2) in order to transmit a "Yellow Alarm" to
the remote terminal equipment.
In this case, the Terminal Equipment intends to insert
the appropriate overhead bits, into the "Transmit
Overhead Data Input Interface" such that the
XRT72L13 will transmit a "Yellow Alarm" to the re-
mote terminal equipment. Recall that, for DS3 appli-
cations, a "Yellow Alarm" is transmitted by setting all
of the "X" bits to "0".
If one assumes that the connection between the Ter-
minal Equipment and the XRT72L13s are as illustrat-
ed in Figure 78 then, Figure 79 presents an illustra-
tion of the signaling that must go on between the Ter-
minal Equipment and the XRT72L13.
FIGURE 79. BEHAVIOR OF "TRANSMIT OVERHEAD DATA INPUT INTERFACE" SIGNALS BETWEEN THE XRT72L13 AND
THE TERMINAL EQUIPMENT (FOR METHOD 2)
TxInClk
TxOHFrame
TxOHEnable
TxOHIns
TxOH
TxOHEnable Pulse # 8
X bit = 0
X bit = 0
Terminal Equipment
samples “TxOHFrame” and
“TxOHEnable” being “HIGH”
Terminal Equipment
responds by asserting
TxOHIns and placing desired
data on TxOH.
XRT72L13 samples TxOH
here.
4.2.3 The Transmit DS3 HDLC Controller
The Transmit DS3 HDLC Controller block can be
used to transport either "Bit-Oriented Signaling (BOS)
or "Message-Oriented Signaling" (MOS) type mes-
sages or both types of messages to the remote termi-
nal equipment. Both BOS and MOS types of HDLC
message processing are discussed in detail below.
4.2.3.1 Bit-Oriented Signaling (or FEAC Mes-
sage) processing via the "Transmit DS3 HDLC
Controller".
The "Transmit DS3 HDLC Controller" block consists
of two major blocks:
• The "Transmit FEAC Processor.
• The "LAPD Transmitter".
This section describes how to operate the "Transmit
FEAC Processor". If the Transmit DS3 Framer is op-
erating in the "C-bit Parity" Framing Format then the
FEAC (Far-End Alarm & Control) bit-field of the DS3
Frame can be used to transmit the FEAC messages
(See Figure 42). The FEAC code word is a 6-bit val-
ue which is encapsulated by 10 framing bits, forming
a 16-bit FEAC message of the form:
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