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XRT79L71
PRELIMINARY
71
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
TxOHInd/
TxGapClk
B9
O
Transmit Overhead Bit Indicator Output/Transmit Gap-Clock Output:
The exact function of this output pin depends upon whether the XRT79L71 has
been configured to operate in the Gapped-Clock Mode or Not.
Non-Gapped Clock Mode - TxOHInd:
This output pin will pulse "High" one bit period prior to the time that the Transmit
Section of the XRT79L71 is processing an Overhead bit. This output pin will be
held "Low" at all other times. The purpose of this output pin is to warn the Sys-
tem-side Terminal Equipment that during the very next bit-period, the XRT79L71
is going to be processing an Overhead bit and will be, during this very next bit-
period, ignoring any data that is applied to the TxSer input pin.
Gapped-Clock Mode - TxGapClk:
If the XRT79L71 has been configured to operate in the Gapped-Clock Mode,
then this particular output pin will function as a demand output clock signal. In
this case, the System-Side Terminal Equipment will be expected to update the
data on the TxSer input pin, upon the rising edge of this particular output signal.
The XRT79L71 will sample and latch the TxSer data, upon the falling edge of the
TxGapClk signal.
NOTE: In the Gapped-Clock Mode, the XRT79L71 will only generate a clock
edge via this output pin whenever the Transmit Payload Data Input
Interface is processing payload data. The XRT79L71 will NOT generate
a clock edge via this output pin whenever the Transmit Payload Data
Input Interface is processing an overhead bit.
TxFrame
B10
O
Transmit End of Frame Output Indicator:
The Transmit Section of the XRT79L71 pulses this output pin "High" for one bit-
period coincident to whenever the Transmit Payload Data Input Interface block is
processing the last bit of a given DS3 frame.
The purpose of this output pin is to alert the System-side Terminal Equipment
that it needs to begin transmission of a new DS3 frame to the Transmit Payload
Data Input Interface block of the XRT79L71 (e.g., to permit the XRT79L71 to
maintain Transmit DS3 Framing alignment control over the System-Side Terminal
Equipment).
TABLE 13: LIST AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT INTERFACE
BLOCK
SIGNAL NAME
PIN/BALL #TYPE
DESCRIPTION