MT9074AL Zarlink Semiconductor, Inc., MT9074AL Datasheet - Page 40

• Manufacturer Part Number: MT9074AL
• Description: T1/E1/J1 Single Chip Transceiver
• Manufacturer: Zarlink Semiconductor, Inc.

MT9074
40
channel is sourced from the transmit message word
in Master Control page 1.
Alarms
The following alarms are detected by the receiver in
T1 mode. Each may generate a maskable interrupt:
•
•
•
The following alarms are detected by the receiver in
E1 mode. Each may generate a maskable interrupt:
•
•
•
•
•
Yellow alarm - in D4 mode there are two possible
yellow alarm signals. If control bit D4SECY is set
low, (page 1H, address 11Hb it 1) the criteria for a
yellow alarm is an excess of ’0’s (more than 285) in
bit position 2 of incoming DS0 channels during an
integration period of 1.5 milliseconds. It is cleared
after more than 3 ’1’s are detected in bit position 2
of normal data in a 1.5 millisecond integration
period. If D4SECY is set high the secondary yellow
alarm is selected. The detection criteria becomes 2
consecutive’1’s in the Sbit position of the 12th
frame. In ESF mode the alarm is set if the pattern
0000000011111111 is received in seven or more
codewords out of ten.;
All Ones - This bit (page 3H, address 11H, bit 3) is
set if less than six zeros are received on the
incoming line data during a 3 ms interval
Loss of Signal - a loss of signal condition occurs
when the receive signal level is lower than 40 dB
below the nominal signal level for at least a
millisecond or when 192 consecutive zeros have
been received. A loss of signal condition will
terminate when than average ones density of at
least 12.5% has been received over a period of
193 contiguous pulse positions starting with a
pulse. The loss of signal is reported in the Receive
Signal Status Word - page 3, address 16H bit 4.
Remote Alarm Indication (RAI) - bit 3 (A) of the
receive NFAS;
Alarm Indication Signal (AIS) - unframed all ones
signal for at least a double frame (512 bits) or two
double frames (1024 bits);
Channel 16 Alarm Indication Signal - all ones
signal in channel 16;
Auxiliary pattern - 101010... pattern for at least 512
bits;
Loss of Signal - a loss of signal condition occurs
when the receive signal level is lower than 20dB or
40 dB (by setting the bit ELOS on page 2) below
the nominal signal level for more than a
millisecond or when more than 192 zeros have
been received in a row. A loss of signal condition
will terminate when an average ones density of at
least 12.5% has been received over a period of
•
The alarm reporting latch (address 12H page 04H)
contains a register whose bits are set high for
selected alarms. These bits stay high until the
register is read. This allows the controller to record
intermittent or sporadic alarm occurrences.
Automatic Alarms
In E1 mode, the transmission of RAI and signaling
multiframe
automatically from control bits ARAI and AUTY
(page 01H, address 10H). When ARAI = 0 and basic
frame synchronization is lost (SYNC = 1), the
MT9074 will automatically transmit the RAI alarm
signal to the far end of the link. The transmission of
this alarm signal will cease when basic frame
alignment is acquired.
When AUTY = 0 and signaling multiframe alignment
is not acquired (MFSYNC = 1), the MT9074 will
automatically transmit the multiframe alarm (Y-bit)
signal to the far end of the link. This transmission will
cease when signaling multiframe alignment is
acquired.
Detected Events and Words
T1 Mode
Severely Errored Frame Event
In T1 mode bit 5 page 3H address 10H toggles
whenever a sliding window detects 2 framing errors
events (Ft or ESF) in a sliding window of 6.
Loop Code Detect
T1.403 defines SF mode line loopback activate and
deactivate codes. These codes are either a framed
or un-framed repeating bit sequence of 00001 for
activation or 001 for deactivation. The standard goes
on to say that these codes will persist for five
seconds or more before the loopback action is taken.
In T1 mode MT9074 will detect both framed and
unframed line activate and de-activate codes even in
the presence of a BER of 3 x 10-3. Line Loopback
Disable Detect - LLDD - in the Alarm Status Word (bit
0 address 11H of page 3H) will be asserted when a
repeating 001 pattern (either framed or unframed)
has persisted for 48 milliseconds. Line Loopback
Enable Detect LLED in the Alarm Status Word will be
asserted when a repeating 00001 pattern (either
255 contiguous pulse positions starting with a
pulse.
Remote signaling Multiframe Alarm - (Y-bit) of the
multiframe alignment signal.
alarms
can
be
made
Data Sheet
to
function