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Bit 3/Local Loopback (LLB). In this loopback, data continues to be transmitted as normal through the transmit
side of the SCT. Data being received at RTIP and RRING are replaced with the data being transmitted. Data in this
loopback passes through the jitter attenuator. See
Figure 3-2 for more details.
0 = loopback disabled
1 = loopback enabled
Bit 4/Line Interface Unit Mux Control (LIUC). This is a software version of the LIUC pin. When the LIUC pin
is connected high, the LIUC bit has control. When the LIUC pin is connected low, the framer and LIU are
separated and the LIUC bit has no effect
0 = if LIUC pin connected high, LIU internally connected to framer block and deactivate the
TPOSI/TNEGI/TCLKI/RPOSI/RNEGI/RCLKI pins
1 = if LIUC pin connected high, disconnect LIU from framer block and activate the
TPOSI/TNEGI/TCLKI/RPOSI/RNEGI/RCLKI pins
LIUC Pin
LIUC Bit
Condition
0
LIU and framer separated
0
1
LIU and framer separated
1
0
LIU and framer connected
1
LIU and framer separated
Bits 5 to 7/Unused, must be set to 0 for proper operation
