XRT72L50 Datasheet, PDF (358/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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TABLE 67: LISTING AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE
SIGNAL NAME
TxNibClk
TxOHInd
TxFrame
TxFrameRef
TxNibFrame
TYPE
DESCRIPTION
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.
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 process-
ing an Overhead bit and will be ignoring any data that is applied to the TxSer input pin.
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 Transmit
E3 framing alignment control over the Terminal Equipment).
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 Fram-
ing alignment control over the XRT72L50.
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
• The Loop-Timing or the TxInClk (Local Timing) Mode
Further, if the XRT72L50 has been configured to operate in the TxInClk mode, then the user has two additional
options.
• The XRT72L50 is the Frame Master (e.g., it dictates when the Terminal Equipment will initiate the
transmission of data within a new E3 frame).
• The XRT72L50 is the Frame Slave (e.g., the Terminal Equipment will dictate when the XRT72L50 initiates
the transmission of a new E3 frame).
Given these three set of options, the Transmit Terminal Input Interface can be configured to operate in one of
the six (6) following modes.
• Mode 1 - Serial/Loop-Timed Mode
• Mode 2 - Serial/Local-Timed/Frame Slave Mode
• Mode 3 - Serial/Local-Timed/Frame Master Mode
• Mode 4 - Nibble/Loop-Timed Mode
• Mode 5 - Nibble/Local-Timed/Frame Slave Mode
• Mode 6 - Nibble/Local-Timed/Frame Master Mode
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