XR72L52 Datasheet, PDF (156/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L52
REV. 1.0.1
xr
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
The behavior of the signals between the XRT72L52 and the Terminal Equipment for DS3 Mode 2 Operation is
illustrated in Figure 35.
FIGURE 35. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L52 AND THE TERMINAL
EQUIPMENT (MODE 2 OPERATION)
Terminal Equipment Signals
DS3_Clock_In
DS3_Data_Out
Tx_Start_of_Frame
DS3_Overhead_Ind
Payload[4702] Payload[4703]
X-Bit
Payload[1]
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxSer
Payload[4702] Payload[4703]
TxFrameRef
TxOH_Ind
X-Bit
Payload[1]
DS3 Frame Number N
DS3 Frame Number N + 1
Note: TxOH_Ind pulses high to
Note: X-Bit will not be processed by the
Transmit Payload Data Input Interface.
denote Overhead Data
(e.g., the X-bit).
Note: TxFrame pulses high to denote
DS3 Frame Boundary.
How to configure the XRT72L52 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 DS3/E3
R/W
R/W
0
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 XRT72L52 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 XRT72L52
The XRT72L52 configured to operate in this mode functions as follows.
Local Timing
The Transmit Section of the XRT72L52 uses the TxInClk signal as its timing reference.
Serial Mode
The XRT72L52 receives the DS3 payload data in a serial manner via the TxSer input pin. The Transmit Pay-
load Data Input Interface within the XRT72L52 latches this data into its circuitry on the rising edge of the TxIn-
Clk input clock signal.
Delineation of outbound DS3 frames (Frame Master Mode)
140