XRT72L50 Datasheet, PDF (255/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
TABLE 43: 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 XRT72L50 in the serial mode, then the Terminal Equipment is
expected to apply the payload data (that is to be transported via the outbound E3 data stream)
to this input pin. The XRT72L50 will sample the data that is at this input pin upon the rising
edge of either the RxOutClk or the TxInClk signal (whichever is appropriate).
NOTE: This signal is only active if the NibIntf input pin is pulled "Low".
TxNib[3:0]
Input
Transmit Nibble-Parallel Payload Data Input pins:
If the user opts to operate the XRT72L50 in the Nibble-Parallel mode, then the Terminal Equip-
ment is expected to apply the payload data (that is to be transported via the outbound E3 data
stream) to these input pins. The XRT72L50 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 NibIntf input pin is pulled "High".
TxInClk
Input
Transmit Section Timing Reference Clock Input pin:
The Transmit Section of the XRT72L50 can be configured to use this clock signal as the Tim-
ing Reference. If the user has made this configuration selection, then the XRT72L50 will use
this clock signal to sample the data on the TxSer input pin.
NOTE: If this configuration is selected, then a 34.368 MHz clock signal must be applied to this
input pin.
TxNibClk
Output Transmit Nibble Mode Output
If the user opts to operate the XRT72L50 in the Nibble-Parallel mode, then the XRT72L50 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 XRT72L50 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
XRT72L50 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 XRT72L50 is going to be pro-
cessing an Overhead bit and will be ignoring any data that is applied to the TxSer input pin.
TxFrame
Output Transmit End of Frame Output Indicator:
The Transmit Section of the XRT72L50 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 E3 frame.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin trans-
mission of a new E3 frame to the XRT72L50 (e.g., to permit the XRT72L50 to maintain Trans-
mit E3 framing alignment control over the Terminal Equipment).
TxFrameRef
Input
Transmit Frame Reference Input:
The XRT72L50 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 E3 frame, upon the rising edge of this signal.
The purpose of this input pin is to permit the Terminal Equipment to maintain Transmit E3
Framing alignment control over the XRT72L50.
TxNibFrame
Output Transmit Frame Boundary Indicator - Nibble/Parallel Interface:
This output pin pulses "High" when the last nibble of a given DS3 or E3 frame is expected at
the TxNib[3:0] input pins.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin trans-
mission of a new DS3 or E3 frame to the XRT72L50.
Operation of the Transmit Payload Data Input Interface
The Transmit Terminal Input Interface is extremely flexible, in that it permits the user to make the following
configuration options.
• The Serial or the Nibble-Parallel Interface Mode
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