Datasheet

DS26303: 3.3V, T1/E1/J1, Short-Haul, Octal Line Interface Unit
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6.7 G.772 Monitor
In this application, only seven LIUs are functional and one LIU is used for nonintrusive monitoring of input and
output of the other seven channels. Channel 1 is used for monitoring channels 2 to 8. G.772 monitoring is
configured by the
GMC register (see Table 5-9). While monitoring with channel 1, the device can be configured in
remote loopback and the monitored signal can be output on TTIP1 and TRING1.
6.8 Loopbacks
The DS26303 provides four loopbacks for diagnostic purposes: analog loopback (ALBC:ALBCn set), digital
loopback (
DLBC:DLBCn set), remote loopback (RLBC:RLBCn set), and dual loopback (DLBC:DLBCn set and
(
RLBC:RLBCn set).
6.8.1 Analog Loopback
The analog output of the transmitter TTIPn and TRINGn is looped back to RTIPn and RRINGn of the receiver. Data
at RTIPn and RRINGn is ignored in analog loopback. See
Figure 6-8.
Figure 6-8. Analog Loopback
Line
Driver
HDB3/
B8ZS
Encoder
O ptional
Jitter
A ttenuator
Transm it
Digital
Transm it
Analog
TCLK
TPOS
TNEG
HDB3/
B8ZS
D ecoder
O ptional
Jitter
A ttenuator
Receive
Digital
Receive
Analog
RCLK
RPOS
RNEG
Rtip
Rring
6.8.2 Digital Loopback
The transmit system data TPOSn, TNEGn, and TCLKn are looped back to output on RCLKn, RPOSn, and RNEGn.
The data input at TPOSn and TNEGn is encoded and output on TTIPn and TRINGn. Signals at RTIPn and
RRINGn are ignored. This loopback is conceptually shown in
Figure 6-9.