XRT72L56 Datasheet, PDF (389/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY
XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
FIGURE 168. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L56 AND THE TERMINAL
EQUIPMENT (E3 MODE 6 OPERATION)
Terminal Equipment Signals
TxInClk
E3_Nib_Clock_In
E3_Data_Out[3:0]
Tx_Start_of_Frame
E3_Overhead_Ind
Payload Nibble [1059]
Overhead Nibble [0]
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxNibClk
TxNib[3:0]
TxNibFrame
Nibble [1059]
Overhead Nibble [0]
TxOH_Ind
Note: TxNibFrame pulses high to denote
E3 Frame Boundary.
E3 Frame Number N
E3 Frame Number N + 1
TxOH_Ind pulses high for 4 Nibble periods
How to configure the XRT72L56 into Mode 6
1. Set the NibInt input pin "High".
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "1X" as illus-
trated below.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt Frame Format
Enable Reset
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
BIT 1
BIT 0
TimRefSel[1:0]
R/W
R/W
1
x
3. Interface the XRT72L56, to the Terminal Equip-
ment, as illustrated in Figure 167.
6.2.2 The Transmit Overhead Data Input Inter-
face
Figure 169 presents a simple illustration of the Trans-
mit Overhead Data Input Interface block within the
XRT72L56.
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