XRT75R12DIB-F Exar Corporation, XRT75R12DIB-F Datasheet - Page 104

• Manufacturer Part Number: XRT75R12DIB-F
• Description: Peripheral Drivers & Components (PCIs) 12 Channel 3.3V-5V temp -45 to 85C
• Manufacturer: Exar Corporation

Specifications of XRT75R12DIB-F

• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 3.3 V to 5 V
• Package / Case: TBGA-420
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

XRT75R12D
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
Whenever these "positive-stuffing" events occur then (for these particular STS-1 SPEs) the SPE will carry only
5591 DS3 data bits (e.g., in this case, only 2 Stuff Opportunity bits will be carrying DS3 data-bits, and the
remaining 7 Stuff Opportunity bits are "stuff" bits).
Figure 47
this condition.
What does this mean at the Destination PTE?
In this case, this DS3 signal (which has now been mapped into an STS-1 data-stream) will be transported
across the SONET network. As this STS-1 signal arrives at the "Destination" PTE, this PTE will extract (or de-
map) this DS3 data from each incoming STS-1 SPE. Now, in this case, most (e.g., 177/178.8) of the incoming
STS-1 SPEs will contain 5592 DS3 data-bits. Therefore, the nominal data rate of the DS3 signal being de-
mapped from SONET will be 44.736Mbps. However, in approximately 1 out of every 178 incoming STS-1
SPEs, the SPE will carry only 5591 DS3 data bits. This means that (during these times) the data rate of the de-
mapped DS3 signal will have an instantaneous frequency that is less than 44.736Mbps. These "excursions" of
the de-mapped DS3 data-rate, from the nominal DS3 frequency can be viewed as occurrences of mapping/de-
mapping jitter with an amplitude of approximately 1UI-pp.
Since this occurrence of "de-mapping" jitter is periodic and occurs once every 22.35ms, we can state that this
jitter has a frequency of 44.7Hz.
We talked about De-Mapping Jitter, What about De-Mapping Wander?
The Telcordia and Bellcore specifications define "Wander" as "Jitter with a frequency of less than 10Hz".
Based upon this definition, the DS3 signal (that is being transported by SONET) will cease to contain jitter and
will now contain "Wander", whenever the frequency offset of the DS3 signal being mapped into SONET is less
than 0.2ppm.
F
MAPPING A
IGURE
47. A
presents an illustration of the STS-1 SPE traffic that will be generated by the "Source" PTE, during
DS3
N
44.736Mbps - 1ppm
I
SIGNAL THAT HAS A BIT RATE OF
LLUSTRATION OF THE
Source
Source
PTE
PTE
STS-1 SPE
DS3 Data
SPE # N
DS3 Data
5592
Bits
5592
Bits
SPE # N+1
DS3 Data
44.736M
DS3 Data
TRAFFIC THAT WILL BE GENERATED BY THE
5592
Bits
5592
Bits
STS-1 SPE Data Stream
100
BPS
- 1
SPE # N+177
PPM
DS3 Data
DS3 Data
5592
Bits
5592
Bits
,
INTO AN
Bit Excluded Here
SPE # N+178
DS3 Data
DS3 Data
DS3 Data
5591
Bits
5591
STS-1
Bits
SPE # N+179
SIGNAL
DS3 Data
DS3 Data
5592
Bits
5592
Bits
S
OURCE
PTE,
REV. 1.0.3
WHEN