
XRT7250
DS3/E3 FRAMER IC
á
REV. 1.1.1
178
Table 33 relates the content of this bit-field to the Bi-
polar Line Code that DS3 Data will be transmitted and
received at.
NOTES:
1. This bit is ignored if the Unipolar mode is selected.
2. This selection also effects the operation of the
Receive DS3 LIU Interface block
4.2.5.2
TxLineClk Clock Edge Selection
The Framer also allows the user to specify whether
the DS3 output data (via TxPOS and/or TxNEG out-
put pins) is to be updated on the rising or falling edg-
es of the TxLineClk signal. The purpose of this fea-
ture is to insure that the Framer will always be able to
output data to the LIU IC, in such a way that the LIU
set-up and hold time requirements can always be
met. This selection is made by writing to bit 2 of the I/
O Control Register, as depicted below.
Table 34 relates the contents of this bit field to the
clock edge of TxClk that DS3 Data is output on the
TxPOS and/or TxNEG output pins.
NOTE: The user will typically make the selection based
upon the set-up and hold time requirements of the Transmit
LIU IC.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7BIT 6BIT 5
BIT 4BIT 3BIT2BIT 1BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/WR/W
R/W
10
1
00
000
TABLE 33: THE RELATIONSHIP BETWEEN BIT 4 (AMI/B3ZS*) WITHIN THE I/O CONTROL REGISTER AND THE BIPOLAR
LINE CODE THAT IS OUTPUT BY THE TRANSMIT DS3 LIU INTERFACE BLOCK
BIT 4BIPOLAR LINE CODE
0
B3ZS
1AMI
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7BIT 6BIT 5BIT 4BIT 3
BIT2BIT 1BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
10
100
XX
0
TABLE 34: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 2RESULT
0
Rising Edge:
Outputs on TxPOS and/or TxNEG are updated on the rising edge of TxLineClk.
See
Figure 70 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
1
Falling Edge:
Outputs on TxPOS and/or TxNEG are updated on the falling edge of TxLineClk.
See
Figure 71 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.