XRT72L50 Datasheet, PDF (154/471 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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The behavior of the signals between the XRT72L50 and the Terminal Equipment for DS3 Mode 2 Operation is
illustrated in Figure 35.
FIGURE 35. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L50 AND THE TERMINAL
EQUIPMENT (MODE 2 OPERATION)
Terminal Equipm ent Signals
DS3_Clock_In
D S3 _ D a ta _O u t
Tx_Start_of_Fram
e
D S 3 _ O v e rh e ad _ In d
Payload[4702] Payload[4703]
XRT 72L 5x T ransm it Payload Data I/F Sig nals
T xIn C lk
TxSer
Payload[4702] Payload[4703]
TxFrameRef
T xO H _ Ind
DS3 Frame Number N
X -Bit
Payload[1]
X - Bit
P aylo a d [1]
DS3 Frame Number N + 1
Note: TxOH_Ind pulses high to denote
Overhead Data (e.g., the X bit).
Note: X - Bit will not be processed by the
Transmit Payload Data Input Interface.
Note: TxFrame pulses high to denote
DS3 Frame Boundary.
How to configure the XRT72L50 to operate in this mode.
1. Set the NibIntf input pin "Low".
2. Set the TimRefSel[1:0] bit-fields within the Framer Operating Mode Register to "01" as depicted below.
Framer Operating Mode Register (Address = 0x00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loop-back
R/W
0
DS3/E3
R/W
0
Internal LOS
Enable
R/W
1
RESET
R/W
0
Interrupt
Enable Reset
R/W
1
Frame Format
R/W
0
TimRefSel[1:0]
R/W
R/W
0
1
3. Interface the XRT72L50 to the Terminal Equipment as illustrated in Figure 34.
4.2.1.3 Mode 3 - The Serial/Local-Timed/Frame-Master 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 Master Mode)
141