DS2155 datasheet(60/262 Pages) DALLAS

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DS2156

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Table 8-A. T1 Alarm Criteria

ALARM

SET CRITERIA

CLEAR CRITERIA

Blue Alarm (AIS)

(Note 1)

When over a 3ms window, five or

fewer 0s are received

When over a 3ms window, six or

more 0s are received

Yellow Alarm (RAI)

D4 Bit 2 Mode

(T1RCR2.0 = 0)

When bit 2 of 256 consecutive

channels is set to 0 for at least 254

occurrences

When bit 2 of 256 consecutive

channels is set to 0 for fewer than

254 occurrences

D4 12th F-Bit Mode

(T1RCR2.0 = 1; this mode is also

referred to as the “Japanese Yellow

Alarm”)

When the 12th framing bit is set to 1

for two consecutive occurrences

When the 12th framing bit is set to

0 for two consecutive occurrences

ESF Mode

When 16 consecutive patterns of

00FF appear in the FDL

When 14 or fewer patterns of 00FF

hex out of 16 possible appear in the

FDL

Red Alarm (LRCL)

(Also referred to as loss of signal)

When 192 consecutive 0s are

received

When 14 or more 1s out of 112

possible bit positions are received

Note 1: The definition of Blue Alarm (or AIS) is an unframed all-ones signal. Blue Alarm detectors should be able to operate properly in the

presence of a 10E-3 error rate and they should not falsely trigger on a framed all-1s signal. Blue Alarm criteria in the DS2156 has been

set to achieve this performance. It is recommended that the RBL bit be qualified with the RLOS bit.

Note 2: ANSI specifications use a different nomenclature than the DS2156 does. The following terms are equivalent:

RBL = AIS

RCL = LOS

RLOS = LOF

RYEL = RAI

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