XRT72L13 Datasheet, PDF (269/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

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PRELIMINARY
XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
Method 1) in order to transmit a "Yellow Alarm" to
the remote terminal equipment.
In this example, the Terminal Equipment intends to in-
sert 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
both of the "X" bits (within each “outbound” DS3
frame) to "0".
If one assumes that the connection between the Ter-
minal Equipment and the XRT72L13 are as illustrated
in Figure 76 then Figure 77 presents an illustration
of the signaling that must go on between the Terminal
Equipment and the XRT72L13.
FIGURE 77. ILLUSTRATION OF THE SIGNAL THAT MUST OCCUR BETWEEN THE TERMINAL EQUIPMENT AND THE
XRT72L13, IN ORDER TO CONFIGURE THE XRT72L13 TO TRANSMIT A "YELLOW ALARM" TO THE "REMOTE TERMI-
NAL EQUIPMENT"
Terminal Equipment/XRT72L13 Interface Signals
TxOHClk
TxOHFrame
TxOHIns
TxOH
0 0- 1
2
3
4
5
6
7
8 8-
X bit = 0
Remaining Overhead Bits with DS3 Frame
X bit = 0
TxOHFrame is sample “high”
Terminal Equipment asserts
“TxOHIns” and data on “TxOH” line
XRT72L13 device samples the TxOHIns and
TxOH signals.
TxOHFrame is sample “high”
Terminal Equipment asserts
“TxOHIns” and data on “TxOH” line
XRT72L13 samples the TxOHIns and
TxOH signals.
In Figure 77 the Terminal Equipment samples the
"TxOHFrame" signal being "high" at "rising clock
edge # 0". At this point, the Terminal Equipment
knows that the XRT72L13 is just about to process the
very first overhead bit within a given "outbound" DS3
frame. Additionally, according to Table 15 , the very
first overhead bit to be processed is the first "X" bit.
In order to facilitate the transmission of the "Yellow
Alarm", the Terminal Equipment must set this "X" bit
to "0". Hence, the Terminal Equipments starts this
data, it will then insert a "0" into the first "X" bit posi-
process by implementing the following steps concur-
rently.
a. Assert the "TxOHIns" input pin by setting it "high".
b. Set the "TxOH" input pin to "0".
After the Terminal Equipment has applied these sig-
nals, the XRT72L13 will sample the data on both the
"TxOHIns" and "TxOH" signals upon the very next
falling edge of "TxOHClk" (designated at "0-" in
Figure 77 . Once the XRT72L13 has sampled this
tion, in the "outbound" DS3 frame.
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