XRT84L38
OCTAL T1/E1/J1 FRAMER
BIT NUMBER
BIT NAME
5-4
Loop-back Select
3
Transmit Line Clock
Inversion
REV. 1.0.1
BIT TYPE
BIT DESCRIPTION
R/W Loop-back Select:
These READ/WRITE bit-fields permit the user to configure any
channel of the framer to operate in different loop-back modes.
Each channel of the framer can operate in three loop-back
modes:
Local Loop-back (LL), Far-End Line Loop-back (FELL) and Pay-
load Loop-back (PL).Local Loop-back connects the transmitter
output of the framer back to the receiver input. All payload data
as well as data link bits and Frame Alignment bits are directed
back into the framer. The Local-Loop-back allows the perfor-
mance of diagnostic tests on the transmitter and receiver to ver-
ify operation of the framer and equipment-side circuitry.
Payload Loop-back also connects the transmitter output of the
framer back to the receiver input. However, only payload data
and Frame Alignment bits are directed back into the framer. The
framer can still transmit data link information to the remote termi-
nal. The Payload Loop-back allows the performance of diagnos-
tic tests on the transmitter and receiver to verify operation of the
framer and equipment-side circuitry. At the same time, the Pay-
load Loop-back allows performance report and test signal identi-
fication message to be sent to remote side.
Far-End Line Loop-back connects the receiver input to the trans-
mit output. Only the LIU interface logic inside the framer can be
examined using this loop-back mode. During the Far-End Line
Loop-back, the Recovered Receive Line Clock will automatically
be the source of the Transmit Line Clock.
When these bits are set to 00:
The framer is operating in normal mode; no loop-back mode is
selected.
When these bits are set to 01:
The framer is operating in Local Loop-back mode.
When these bits are set to 10:
The framer is operating in Far-End Line Loop-back mode.
When these bits are set to 11:
The framer is operating in Payload Loop-back mode.
R/W Transmit Line Clock Inversion:
This READ/WRITE bit-field permits the user to select which
edge of the Transmit Line Clock will data transition occur.
When this bit is set to zero:
The transmit data transition occurs at rising edge of the Transmit
Line Clock. The user should program the LIU device to sample
data at falling edge of the Transmit Line Clock.
When this bit is set to one:
The transmit data transition occurs at falling edge of the Transmit
Line Clock. The user should program the LIU device to sample
data at rising edge of the Transmit Line Clock.
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