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DS34T102 Datasheet - Page 123

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____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
Table 10-48. E1 Alarm Criteria
ALARM
SET CRITERIA
255 or 2048 consecutive zeros
LOS
received (determined by
RLS1.RLOSC)
LOF
Fewer than three zeros in two
AIS
frames (512 bits)
Bit 3 of non-FAS frame set to one
RAI
three consecutive occasions
Table 10-49. E1 LOF Sync and Resync Criteria
FRAME OR
MULTIFRAME
SYNC CRITERIA
TYPE
FAS present in frames N
FAS
and N+2 and FAS not
present in frame N+1.
Two valid multiframe
CRC-4
alignment words found
within 8ms.
Valid multiframe alignment
CAS
word found.
10.11.6.4 T1 AIS-CI and RAI-CI Detection
AIS-CI is a repetitive pattern with a 1.26 second period. It consists of 1.11 seconds of unframed all ones pattern
followed by 0.15 seconds of all ones modified by the AIS-CI signature. The AIS-CI signature is a repetitive pattern
6176 bits in length in which, if the first bit is numbered bit 0, bits 3088, 3474 and 5790 are logical zeros and all
other bits in the pattern are logical ones (see ANSI T1.403). AIS-CI is an unframed pattern, and therefore is defined
for all T1 framing formats. The RLS7-T1.RAIS-CI status bit is set when the AIS-CI pattern has been detected while
RRTS1.RAIS is set. RAIS-CI is a latched bit that should be cleared by the CPU after it is read. RAIS-CI is set again
approximately every 1.26 seconds as long as the AIS-CI condition is present.
RAI-CI is a repetitive pattern within the ESF data link with a period of 1.08 seconds. It consists of 0.99 seconds of
“00000000 11111111” (right-to-left) followed by 90 ms of “00111110 11111111”. The RLS7-T1.RRAI-CI status bit is
set when a bit oriented code of “00111110 11111111” is detected while RRTS1.RRAI is set. The RRAI-CI detector
uses the Rx BOC filter bits (RBOCC.RBF[1:0]) to determine the integration time for RAI-CI detection. Like RAIS-CI,
the RRAI-CI bit is latched and should be cleared by the CPU after it is read. RRAI-CI is set again approximately
every 1.1 seconds as long as the RAI-CI condition is present. It may be useful to enable the 200ms ESF RAI
integration time by setting RCR2-T1.RAIIE=1 in networks that utilize RAI-CI.
10.11.7 E1 Automatic Alarm Generation
In E1 mode the transmit formatter can be programmed to automatically transmit AIS or RAI in response to events
detected by the receive framer. When automatic AIS generation is enabled (TCR2-E1.AAIS=1), if the receive
framer detects any of the following conditions then the transmit formatter automatically transmits AIS: Rx loss of
signal, Rx loss of frame synchronization, or Rx AIS alarm.
CLEAR CRITERIA
At least 32 ones received in 255 bit
times
See
Table
10-49.
Three or more zeros in two frames
(512 bits)
Bit 3 of non-FAS frame set to zero for
three consecutive occasions
RESYNC CRITERIA
If RCR1-E1:FRC=0, three consecutive incorrect
FAS.
If RCR1-E1:FRC=1, three consecutive incorrect
FAS or three consecutive incorrect bit 2 of non-FAS
frame
915 or more errored CRC-4 blocks out of 1000.
Two consecutive multiframe alignment words
received in error or, for a period of one multiframe,
all the bits in timeslot 16 are zero.
ITU SPEC
G.775 4.2
O.162 1.6.1.2
O.162 2.1.4
ITU SPEC
G.706
4.1.1
4.1.2
G.706 4.2
and 4.3.2
G.732 5.2
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