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XRT79L71
PRELIMINARY
435
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
TxOHInd/TxGap-
Clk
B9
O
Transmit Overhead Bit Indicator Output/Transmit Gap-Clock Output:
The function of this output pin depends upon whether or not the XRT79L71
has been configured to operate in the Gapped-Clock Mode.
Non-Gapped Clock Mode - TxOHInd:
This output pin will pulse "high" one bit period prior to the time that the "Trans-
mit 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 System-Side Terminal Equipment that during the very next bit-period, the
XRT79L71 is going to be processing an Overhead bits 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 E3 frame.
The purpose of this output pin is to alert the System-Side Terminal Equipment
that it needs to begin transmission of a new E3 frame to the Transmit Payload
Data Input Interface block of the XRT79L71 (e.g., to permit the XRT79L71 to
maintain Transmit E3 Framing alignment control over the System-Side Termi-
nal Equipment).
TABLE 56: LIST AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT INTERFACE
BLOCK
SIGNAL NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION