XRT75L00D Datasheet, PDF (89/92 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

REV. 1.0.2
XRT75L00D
E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
that are responsible for acquiring and maintaining DS1 or DS3 frame synchronization (with these DS1 or DS3
data-streams that have been de-mapped from SONET) must have re-acquired DS1 or DS3 frame
synchronization within 50ms" after APS has been initiated."
The LIU was designed such that the DS3 signals that it receives from a SONET Mapper device and processes
will comply with the Category I Intrinsic Jitter requirements per Telcordia GR-253-CORE.
Reference 1 documents some APS Recovery Time testing, which was performed to verify that the Jitter
Attenuator blocks (within the LIU) device that permit it to comply with the Category I Intrinsic Jitter
Requirements (for DS3 Applications) per Telcordia GR-253-CORE, do not cause it to fail to comply with the
"APS Completion Time" requirements per Section 5.3.3.3 of Telcordia GR-253-CORE. However, Table 20
presents a summary of some APS Recovery Time requirements that were documented within this test report.
TABLE 20: MEASURED APS RECOVERY TIME AS A FUNCTION OF DS3 PPM OFFSET
DS3 PPM OFFSET (PER W&G ANT-20SE)
MEASURED APS RECOVERY TIME (PER LOGIC ANALYZER)
-99 ppm
1.25ms
-40ppm
1.54ms
-30 ppm
1.34ms
-20 ppm
1.49ms
-10 ppm
1.30ms
0 ppm
1.89ms
+10 ppm
1.21ms
+20 ppm
1.64ms
+30 ppm
1.32ms
+40 ppm
1.25ms
+99 ppm
1.35ms
NOTE: The APS Completion (or Recovery) time requirement is 50ms.
Configuring the LIU to be able to comply with the SONET APS Recovery Time Requirements of 50ms
Quite simply, the user can configure a given Jitter Attenuator block (associated with a given channel) to (1)
comply with the "APS Completion Time" requirements per Telcordia GR-253-CORE, and (2) also comply with
the "Category I Intrinsic Jitter Requirements per Telcordia GR-253-CORE (for DS3 applications) by making
sure that Bit 4 (SONET APS Recovery Time Disable Ch_n), within the Jitter Attenuator Control Register is set
to "0" as depicted below.
JITTER ATTENUATOR CONTROL REGISTER
Channel 0 Address Location = 0x07, Channel 1 Address Location = 0x0F, Channel 2 Address Location = 0x17
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
SONET APS
Recovery
Time Disable
Ch_n
JA RESET
Ch_n
JA1 Ch_n JA in Tx Path JA0 Ch_n
Ch_n
R/O
R/O
R/O
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
1
1
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