MT9074
Advance Information
will
become
unfrozen
when
multiframe
within the MT9074. Sbit information and the DL
originate at the point of loopback.
synchronization is acquired.
When the CAS signalling interrupt is unmasked
(page 01H, address 1EH, SIGI=0), pin IRQ (pin 12 in
PLCC, 85 in MQFP) will become active when a
signalling nibble state change is detected in any of
the 30 receive channels.
MT9074
DSTi
System
DSTo
Tx
Rx
DS1
In CCS mode the data transmit on channel 16 is
either sourced from channel 16 data on DSTi or from
the pin CSTi. Data received from channel 16 is
clocked out on CSTo (pin 5 in PLCC, pin 70 in
MQFP). By dividing down the extracted 2.048 MHz
clock.
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.
MT9074
Loopbacks
DSTi
System
DSTo
Tx
Rx
DS1
In order to meet PRI Layer 1 requirements and to
assist in circuit fault sectioning, the MT9074 has six
loopback functions. These are as follows:
f) Local and remote time slot 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.
a) Digital loopback (DSTi to DSTo at the framer/LIU
interface). Bit DLBK = 0 normal; DLBK = 1 activate.
MT9074
DSTi
System
DSTo
Tx
DS1
MT9074
DSTi
Tx
DS1
Rx
System
b) Remote loopback (RTIP and RRING to TTIP and
TRING respectively at the DS1 side). Bit RLBK = 0
normal; RLBK = 1 activate.
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.
MT9074
Tx
DS1
Rx
System
DSTo
c) ST-BUS loopback (DSTi to DSTo at the system
side). Bit SLBK = 0 normal; SLBK = 1 activate.
Performance Monitoring
Error Counters
MT9074
Tx
DS1
DSTi
System
DSTo
In T1 mode, MT9074 has eight error counters, which
can be used for maintenance testing, an ongoing
measure of the quality of a DS1 link and to assist the
designer in meeting specifications such as TR62411
and T1.403. All counters can be preset or cleared by
writing to the appropriate locations.
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
34
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