XRT72L13 Datasheet, PDF (246/370 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
TABLE 12: LISTING AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE "TRANSMIT PAYLOAD DATA INPUT
INTERFACE
SIGNAL NAME TYPE
DESCRIPTION
TxSer
Input
Transmit Serial Payload Data Input Pin:
If the user opts to operate the XRT72L13 in the "Serial" mode, then the Terminal Equipment is
expected to apply the payload data (that is to be transported via the "outbound" DS3 data
stream) to this input pin. The XRT72L13 will sample the data that is at this input pin; upon the
rising edge either the "RxOutClk" or the "TxInClk" signal (whichever is appropriate).
NOTE: This signal is only active if the "NibInt" input pin is pulled "low".
TxNib[3:0]
Input
Transmit Nibble-Parallel Payload Data Input pins:
If the user opts to operate the XRT72L13 in the "Nibble-Parallel" mode, then the Terminal
Equipment is expected to apply the payload data (that is to be transported via the "outbound"
DS3 data stream) to these input pins. The XRT72L13 will sample the data that is at these
input pins; upon the rising edge of the "TxNibClk" signal.
NOTE: These pins are only active if the "NibInt" input pin is pulled "high".
TxInClk
Input
Transmit Section Timing Reference Clock Input pin:
The Transmit Section of the XRT72L13 can be configured to use this clock signal as the "Tim-
ing Reference". If the user has made this configuration selection, then the XRT72L13 will use
this clock signal to sample the data on the TxSer input pin.
NOTE: If the user has made this configuration selection; then he/she must insure that a 44.736
MHz clock signal is applied to this input pin.
TxNibClk
Output Transmit Nibble Mode Output
If the user opts to operate the XRT72L13 in the "Nibble-Parallel" mode, then the XRT72L13
will derive this clock signal from the selected "Timing Reference" for the Transmit Section of
the chip (e.g., either the TxInClk or the RxLineClk signals).
The XRT72L13 will use this signal to sample the data on the "TxNib[3:0]" input pins.
TxOHInd
Output Transmit Overhead Bit Indicator Output:
This output pin will pulse "high" one-bit period prior to the time that the Transmit Section of the
XRT72L13 will be processing an Overhead bit. The purpose of this output pin is to warn the
Terminal Equipment that, during the very next bit-period, the XRT72L13 is going to be pro-
cessing an "Overhead" bit and will be ignoring any data that is applied to the "TxSer" input pin.
For DS3 applications, this output pin is only active if the XRT72L13 is operating in the "Serial"
Mode. This output pin will be pulled "low" if the device is operating in the "Nibble-Parallel"
Mode.
TxFrame
Output Transmit "End of Frame" Output Indicator:
The Transmit Section of the XRT72L13 will pulse this output pin "high" (for one bit-period),
when the Transmit Payload Data Input Interface is processing the last bit of a given DS3 frame.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin trans-
mission of a new DS3 frame to the XRT72L13 (e.g., to permit the XRT72L13 to maintain
Transmit DS3 framing alignment control over the Terminal Equipment).
TxFrameRef
Input
Transmit Frame Reference Input:
The XRT72L13 permits the user to configure the Transmit Section to use this input pin as a
"frame reference". If the user makes this configuration selection, then the Transmit Section will
initiate its transmission of a new DS3 frame, upon the rising edge of this signal.
The purpose of this input pin is to permit the Terminal Equipment to maintain Transmit DS3
Framing alignment control over the XRT72L13.
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