XRT7250 Datasheet, PDF (371/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
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FIGURE 168. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT7250 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]
XRT7250 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 XRT7250 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 XRT7250, 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
XRT7250.
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