XRT72L50 Datasheet, PDF (152/471 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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3. Interface the XRT72L50 to the Terminal Equipmen as illustrated in Figure 32.
The XRT72L50 cannot support the Framer Local Loop-back Mode of operation when operating in the Loop-
Timing Mode. The XRT72L50 must be configured into any of the following modes prior to configuring the
Framer Local Loop-back Mode.
• Mode 2 - Serial/Local-Timed/Frame-Slave Mode.
• Mode 3 - Serial/Local-Timed/Frame-Master Mode.
• Mode 5 - Nibble-Parallel/Local-Timed/Frame-Slave Mode.
• Mode 6 - Nibble-Parallel/Local-Timed/Frame-Master Mode.
NOTE: For more detailed information on Framer Local Loop-back Mode of operation, see Section 7.0.
4.2.1.2 Mode 2 - The Serial/Local-Timed/Frame-Slave Mode Behavior of the XRT72L50
The XRT72L50 configured to operate in this mode functions as follows.
Local-Timing
The Transmit Section of the XRT72L50 uses the TxInClk signal as its timing reference.
Serial Mode
The XRT72L50 receives the DS3 payload data in a serial manner via the TxSer input pin. The Transmit
Payload Data Input Interface within the XRT72L50 latches this data into its circuitry on the rising edge of the
TxInClk input clock signal.
Delineation of outbound DS3 frames (Frame Slave Mode)
The Transmit Section of the XRT72L50 uses the TxInClk input as its timing reference and the TxFrameRef
input signal as its framing reference. The Transmit Section of the XRT72L50 initiates frame generation upon
the rising edge of the TxFrameRef input signal.
Sampling of payload data from the Terminal Equipment
In Mode 2, the XRT72L50 samples the data at the TxSer input pin on the rising edge of TxInClk.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L50 to the Terminal Equipment
for Mode 2 Operation
This is illustrated in Figure 34.
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