DS26521 datasheet(54/258 Pages) MAXIM

54 / 258 page

DS26521 Single T1/E1/J1 Transceiver

54 of 258

Table 8-19. T1 Alarm Criteria

ALARM

SET CRITERIA

CLEAR CRITERIA

AIS

(Blue Alarm) (See Note 1)

When over a 3ms window, 4 or

fewer zeros are received.

When over a 3ms window, 5 or

more zeros are received.

1) D4 Bit 2 Mode

(T1RCR2.0 = 0)

When bit 2 of 256 consecutive

channels is set to zero for at least

254 occurrences.

When bit 2 of 256 consecutive

channels is set to zero for less than

254 occurrences.

2) D4 12th F-Bit Mode

(T1RCR2.0 = 1)

(Note: This mode is

also referred to as the

“Japanese Yellow

Alarm.”)

When the 12th framing bit is set to

one for two consecutive

occurrences.

When the 12th framing bit is set to

zero for two consecutive

occurrences.

RAI

(Yellow

Alarm)

3) 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.

LOS

(Loss of Signal)

(Note: This alarm is also referred to

as receive carrier loss (RCL).)

When 192 consecutive zeros are

received.

When 14 or more ones out of 112

possible bit positions are received

starting with the first one received.

Note 1:

The definition of the Alarm Indication Signal (Blue Alarm) is an unframed all-ones signal. AIS 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-ones signal. The AIS alarm criteria

in the DS26521 has been set to achieve this performance. It is recommended that the RAIS bit be qualified with the RLOF bit.

Note 2:

The following terms are equivalent:

RAIS = Blue Alarm

RLOS = RCL

RLOF = Loss of Frame (conventionally RLOS for Dallas Semiconductor devices)

RRAI = Yellow Alarm

8.9.8

E1 Automatic Alarm Generation

The device can be programmed to automatically transmit AIS or remote alarm. When automatic AIS generation is

enabled (TCR2.6 = 1), the device monitors the receive-side framer to determine if any of the following conditions

are present: loss of receive frame synchronization, AIS alarm (all ones) reception, or loss of receive carrier (or

signal). If any one (or more) of these conditions is present, the framer forces an AIS.

When automatic RAI generation is enabled (TCR2.5 = 1), the framer monitors the receive side to determine if any

of the following conditions are present: loss of receive frame synchronization, AIS alarm (all ones) reception, loss of

receive carrier (or signal), or if CRC-4 multiframe synchronization cannot be found within 128ms of FAS

synchronization (if CRC-4 is enabled). If any one (or more) of the above conditions is present, the framer transmits

an RAI alarm. RAI generation conforms to ETS 300 011 and ITU-T G.706 specifications.

Note: It is an illegal state to have both automatic AIS generation and automatic remote alarm generation enabled

at the same time.

8.9.8.1 Receive AIS-CI and RAI-CI Detection

AIS-CI is a repetitive pattern of 1.26 seconds. It consists of 1.11 seconds of an unframed all-ones pattern and 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 (T1.403). AIS-CI is an unframed pattern, so it is defined for all T1 framing formats. The

RAIS-CI bit is set when the AIS-CI pattern has been detected and RAIS (RRTS1.2) is set. RAIS-CI is a latched bit

that should be cleared by the host when read. RAIS-CI continues to set approximately every 1.2 seconds that the

condition is present. The host needs to poll the bit in conjunction with the normal AIS indicators to determine when

the condition has cleared.

DS26521 Datasheet(PDF) 54 Page - Maxim Integrated Products

DS26521 Datasheet(HTML) 54 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL