XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
208
The following table relates the value of this bit field to
the Transmit DS3 Framer I/O Mode.
Note:
1.
The default condition is the Bipolar Mode.
This selection also affects the operation of the
Receive DS3 Framer block
2.
6.4.4.5.0.1
Please see Section 6.4.3.5
Unipolar Mode Line Code
6.4.4.5.0.2
If the user chooses to operate the UNI in the Bipolar
Mode, then he/she can choose to transmit the DS3
data-stream via the AMI (Alternate Mark Inversion) or
the B3ZS Line Codes. The definition of AMI and
B3ZS line codes follow.
The AMI Line Code
AMI or Alternate Mark Inversion, means that consec-
utive “one’s” pulses (or marks) will be of opposite
Bipolar Mode Line Codes
6.4.4.5.0.2.1
polarity with respect to each other. The line code
involves the use of three different amplitude levels:
+1, 0, and -1. +1 and -1 amplitude signals are used
to represent one’s (or mark) pulses and the “0” ampli-
tude pulses (or the absence of a pulse) are used to
represent zeros (or space) pulses. The general rule
for AMI is: if a given “mark” pulse is of positive polarity,
then the very next “mark” pulse will be of negative
polarity and vice versa. This alternating-polarity rela-
tionship exists between two consecutive mark pulses,
independent of the number of ‘zeros’ that may exist
between these two pulses. Figure 56 presents an
illustration of the AMI Line Code as would appear at
the TxPOS and TxNEG pins of the UNI, as well as
the output signal on the line.
UNI I/O Control Register (Address = 01h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
LOC Enable
Test Mode
Interrupt
Enable
Reset
AMI/B 325*
Unipolar/
Bipolar
TxCLK Inv
RxCLK Inv
Reframe
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
T
ABLE
41: T
HE
R
ELATIONSHIP
BETWEEN
THE
CONTENT
OF
B
IT
3 (U
NIPOLAR
/B
IPOLAR
*)
WITHIN
THE
UNI I/O
C
ONTROL
R
EGISTER
AND
THE
T
RANSMIT
DS3 F
RAMER
L
INE
I
NTERFACE
O
UTPUT
M
ODE
B
IT
3
T
RANSMIT
DS3 F
RAMER
L
INE
I
NTERFACE
O
UTPUT
M
ODE
0
Bipolar Mode: AMI or B3ZS Line Codes are Transmitted and Received
1
Unipolar (Single Rail) mode of transmission and reception of DS3 data is selected.
F
IGURE
56. I
LLUSTRATION
OF
AMI L
INE
C
ODE
Data
TxPOS
TxNEG
Line Signal
1 0
1 1
0 0
0
1
0
1 1
1
0
1
0 1
0
0 1
1 0
0
1
1
1
0
0
1