XRT74L73 Datasheet, PDF (306/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
TABLE 63: A LISTING OF THE OVERHEAD BITS WITHIN THE E3 FRAME, AND THEIR POTENTIAL SOURCES
OVERHEAD BIT
INTERNALLY GENERATED
ACCESSIBLE VIA THE TRANSMIT OVERHEAD
DATA INPUT INTERFACE
BUFFER/REGISTER
ACCESSIBLE
FAS Signal - Bit 9
Yes
Yes
Yes*
FAS Signal - Bit 8
Yes
Yes
Yes
FAS Signal - Bit 7
Yes
Yes
Yes*
FAS Signal - Bit 6
Yes
Yes
Yes*
FAS Signal - Bit 5
Yes
Yes
Yes
FAS Signal - Bit 4
Yes
Yes
Yes
FAS Signal - Bit 3
Yes
Yes
Yes
FAS Signal - Bit 2
Yes
Yes
Yes
FAS Signal - Bit 1
Yes
Yes
Yes
FAS Signal - Bit 0
Yes
Yes
Yes
A Bit
Yes
Yes
Yes
N Bit
Yes
Yes
Yes
NOTES:
1. The XRT74L73 contains mask register bits that
permit the user to alter the state of the internally
generated value for these bits.
2. The Transmit LAPD Controller/Buffer can be con-
figured to be the source of the N bits, within the out-
bound E3 data stream.
The Transmit Overhead Data Input Interface permits
the user to insert overhead data into the outbound E3
frames via the following two different methods.
• Method 1 - Using the TxOHClk clock signal
• Method 2 - Using the TxInClk and the TxOHEnable
signals.
Each of these methods are described below.
5.2.2.1 Method 1 - Using the TxOHClk Clock
Signal
The Transmit Overhead Data Input Interface consists
of the five signals. Of these five (5) signals, the fol-
lowing four (4) signals are to be used when imple-
menting Method 1.
• TxOH
• TxOHClk
• TxOHFrame
• TxOHIns
Each of these signals are listed and described below.
Table 64 .
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