XRT79L71
PRELIMINARY
585
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
1.
Whenever the XRT79L71 is configured to operate in the "LIU Digital Local Loop-back" Mode, the
"Transmit Output" line signal MAY still be output to the remote terminal equipment (depending upon the
state of the "TxON" bit-field - see Note 3, below). A replica of this "Transmit Output" signal will also be
routed into the Receive Path of the device.
2.
Whenever the XRT79L71 is configured to operate in the "LIU Digital Local Loop-back" Mode, then it will
ignore any data that is being applied to the RTIP/RRING input pins.
3.
In contrast to the "LIU Analog Local Loop-back" Mode, the "LIU Digital Local Loop-back" Mode will NOT
be broken (e.g., this loop-back mode will still function) even if the user sets Bit 0 (TxON), within the "LIU
Transmit APS/Redudancy Control" Register to "0" as depicted below.
Configuring the XRT79L71 to operate in the "LIU Digital Local Loop-back" Mode
Ton configure the XRT79L71 to operate in the "LIU Digital Local Loop-back" Mode execute the following steps.
STEP 1 - Make sure that the XRT79L71 is operating in the "Local-Timing" Mode.
This is accomplished by setting Bits 1 and 0 (TimRefSel[1:0]) within the "Framer Operating Mode" Register to
some value other than [0, 0].
STEP 2 - Configure the XRT79L71 to operate in the "LIU Digital Loop-back" Mode
This is accomplished by setting Bits 4 (LIU Remote Loop-back Mode) and 3 (LIU Local Loop-back Mode)
within the "LIU Control" Register to the value [1, 1], as depicted below
7.1.3
The LIU Remote Loop-back Mode
LIU Transmit APS/Redundancy Control Register (Address = 0x1300)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
TxON
R/O
R/W
0
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framer
Local
Loop Back
IsDS3
Internal
LOS
Enable
RESET
Direct
Map
ATM
Frame
Format
TimRefSel[1:0]
R/W
0
1
0
1
0
X
LIU Control Register (Address = 0x1306)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
SFM
Clock Out
Enable
SFM
Enable
LIU
Remote
Loop-back
Mode
LIU
Local
Loop-back
Mode
Unused
R/O
R/W
R/O
0
1
0