
XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
130
The user can configure the UNI chip to operate in the
Line Loopback mode, by writing the appropriate data
to the UNI Operating Mode Register (Address = 00h),
as depicted below.
Writing a “1” to bit 7 of the UNI Operating Mode Reg-
ister, configures the UNI to operate in the “Line Loop-
back” mode. Writing a “0” to this bit-field disables the
Line Loopback mode.
4.1.2
When the UNI chip is configured to operate in the
“PLCP Loopback” mode, the PLCP frames, that have
been generated by the Transmit PLCP Processor, will
be routed directly (internally) to the Receive PLCP
Processor. Figure 24 presents an illustration of the
UNI chip operating in the PLCP Loopback mode.
The PLCP Loopback Mode
The user can configure the UNI chip to operate in the
“PLCP Loopback” mode, by writing the appropriate
data to the UNI Operating Mode Register (Address =
00h), as depicted below.
Writing a “1” to bit 5 of the UNI Operating Mode Reg-
ister, configures the UNI to operate in the PLCP
Loopback mode. Writing a “0” to this bit-field disables
the PLCP Loopback mode.
4.1.3
When the UNI is configured to operate in the “Cell
Loopback” Mode, then ATM cells that are delineated
and pass through the Receive Cell Processor will be
The Cell Loopback Mode
UNI Operating Mode Register (Address = 00h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Line Loopback
Cell Loopback
PLCP Loopback
Reset
Direct-Mapped ATM
C-Bit/M13
TimRefSel[1, 0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
F
IGURE
24. A
N
I
LLUSTRATION
OF
THE
UNI
CHIP
OPERATING
IN
THE
PLCP L
OOPBACK
M
ODE
.
UNI Chip
Tx
Utopia
Tx PLCP
Processor
Tx DS3
Framer
Rx DS3
Framer
Rx PLCP
Processor
Rx
Utopia
Tx Cell
Processor
Rx Cell
Processor
PLCP Loopback
UNI Operating Mode Register (Address = 00h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Line Loopback
Cell Loopback
PLCP Loopback
Reset
Direct-Mapped ATM
C-Bit/M13
TimRefSel[1, 0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W