Datacom DM991C, Product Manual

Page: 18 / 89

Product Manual - DM991 Series V Family - 204.4092.08 18
Bit Name Description
1-14 sw1-sw14 Frame Sync Word
15 fbit1/losd Fixed Indicator bit #1 (Loss of Signal)
16 fbit2/sega Fixed Indicator bit #2 (Segment Anomaly)
17 -> k+16 b1 Payload block #1
K + 17 eoc01 EOC bit #1
K + 18 eoc02 EOC bit #2
K + 19 eoc03 EOC bit #3
K + 20 eoc04 EOC bit #4
K + 21 crc1 Cyclic Redundancy Check #1
K + 22 crc2 Cyclic Redundancy Check #2
K + 23 fbit3/ps Fixed Indicator bit #3 (Power Status)
K + 24 sbid1 Stuff bit ID #1
K + 25 eoc05 EOC bit #5
K + 26 eoc06 EOC bit #6
k + 27 -> 2k + 26 b2 Payload block #2
2k + 27 eoc07 EOC bit #7
2k + 28 eoc08 EOC bit #8
2k + 29 eoc09 EOC bit #9
2k + 30 eoc10 EOC bit #10
2k + 31 crc3 Cyclic Redundancy Check #3
2k + 32 crc4 Cyclic Redundancy Check #4
2k + 33 fbit4/segd Fixed Indicator bit #4 (Segment Defect)
2k + 34 eoc11 EOC bit #11
2k + 35 eoc12 EOC bit #12
2k + 36 sbid2 Stuff bit ID #2
2k + 37 -> 3k + 36 b3 Payload block #3
3k + 37 eoc13 EOC bit #13
3k + 38 eoc14 EOC bit #14
3k + 39 eoc15 EOC bit #15
3k + 40 eoc16 EOC bit #16
3k + 41 crc5 Cyclic Redundancy Check #5
3k + 42 crc6 Cyclic Redundancy Check #6
3k + 43 eoc17 EOC bit #17
3k + 44 eoc18 EOC bit #18
3k + 45 eoc19 EOC bit #19
3k + 46 eoc20 EOC bit #20
3k + 47 -> 4k + 46 b4 Payload block #4
4k + 47 stb1 Stuff bit #1
4k + 48 stb2 Stuff bit #2
4k + 49 stb3 Stuff bit #3
Table 8. G.shdsl Frame Structure
During the data mode, link failures can occur. Such failures are monitored and reported to the user as
follows:
3.4.2. CRC Anomaly
A CRC anomaly shall be declared when the received CRC6 information is different from the CRC6
generated on the received data. The CRC6 bits are part of the previous G.shdsl frame. A discrepancy
between the received CRC6 value and the evaluated CRC6 on the interface indicates that an error
occurred in some bit (or bits) of the frame, but it does not indicate how many, or which bits were in error.
The interface status LED will blink once every second, remaining ON the most of the time while a CRC
error is showing up.
3.4.3. Loop Attenuation Defect
A loop attenuation defect occurs when the line displays an attenuation that exceeds the programmed
threshold. The standard limit for the DM991 G.shdsl interface is 35 dB.