MT9076
Preliminary Information
12.0 Loopbacks
In order to meet PRI Layer 1 requirements and to assist in circuit fault sectioning, the MT9076 has six loopback
functions. These are as follows:
a) Digital loopback (DSTi to DSTo at the framer/LIU interface). Bit DLBK = 0 normal; DLBK = 1 activate.
MT9076
DSTi
System
DSTo
Tx
Line
b) Remote loopback (RTIP and RRING to TTIP and TRING respectively at the Line side). Bit RLBK = 0 normal;
RLBK = 1 activate.
MT9076
Tx
Line
Rx
System
DSTo
c) ST-BUS loopback (DSTi to DSTo at the system side). Bit SLBK = 0 normal; SLBK = 1 activate.
MT9076
Tx
Line
DSTi
System
DSTo
d) Payload loopback (RTIP and RRING to TTIP and TRING respectively at the system side). Bit PLBK = 0
normal; PLBK = 1 activate. The payload loopback is effectively a physical connection of DSTo to DSTi
within the MT9076. Sbit information and the DL originate at the point of loopback.
MT9076
DSTi
System
DSTo
Tx
Rx
Line
e) Metallic Loopback. MLBK = 0 normal; MLBK = 1 activate, will isolate the external signals RTIP and RRING
from the receiver and internally connect the analog output TTIP and TRING to the receiver analog input.
MT9076
DSTi
System
DSTo
Tx
Rx
Line
f) Per time slot local and remote loopback. Remote time slot loopback control bit RTSL = 0 normal; RTSL = 1
activate, will loop around transmit ST-BUS time slots to the DSTo stream. Local time slot loopback bits LTSL
= 0 normal; LTSL = 1 activate, will loop around receive PCM 30 time slots towards the remote PCM 30 end.
MT9076
Tx
Line
Rx
DSTi
System
DSTo
The digital, remote, ST-BUS, payload and metallic loopbacks are located on page 1, address 15H - Coding and
Loopback Control Word. The remote and local time slot loopbacks are controlled through control bits 5 and 4 of
the Per Time Slot Control Words, pages 7H and 8H.
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MITEL [ MITEL NETWORKS CORPORATION ]
