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參數(shù)資料
| 型號(hào)： | XRT75R12DIB |
| 廠商： | EXAR CORP |
| 元件分類： | 數(shù)字傳輸電路 |
| 英文描述： | TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER |
| 中文描述： | DATACOM, PCM TRANSCEIVER, PBGA420 |
| 封裝： | 35 X 35 MM, TBGA-420 |
| 文件頁數(shù)： | 103/131頁 |
| 文件大?。?/td> | 717K |
| 代理商： | XRT75R12DIB |
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PRELIMINARY
XRT75R12D
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
REV. P1.0.1
98
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.
8.3
Jitter/Wander due to Pointer Adjustments
In the previous section, we described how a DS3 signal is asynchronously-mapped into SONET, and we also
defined "Mapping/De-mapping" jitter. In this section, we will describe how occurrences within the SONET
network will induce jitter/wander within the DS3 signal that is being transported across the SONET network.
In order to accomplish this, we will discuss the following topics in detail.
The concept of an STS-1 SPE pointer
The concept of Pointer Adjustments
The causes of Pointer Adjustments
How Pointer Adjustments induce jitter/wander within a DS3 signal being transported by that SONET network.
8.3.1
The Concept of an STS-1 SPE Pointer
As mentioned earlier, the STS-1 SPE is not aligned to the STS-1 frame boundaries and is permitted to "float"
within the Envelope Capacity. As a consequence, the STS-1 SPE will often times "straddle" across two
F
IGURE
47. A
N
I
LLUSTRATION
OF
THE
STS-1 SPE
TRAFFIC
THAT
WILL
BE
GENERATED
BY
THE
S
OURCE
PTE,
WHEN
MAPPING
A
DS3
SIGNAL
THAT
HAS
A
BIT
RATE
OF
44.736M
BPS
- 1
PPM
,
INTO
AN
STS-1
SIGNAL
PTE
Source
44.736Mbps - 1ppm
5592
DS3 Data
Bits
5592
DS3 Data
Bits
SPE # N
SPE # N+1
5592
DS3 Data
Bits
SPE # N+177
5591
DS3 Data
Bits
5592
DS3 Data
Bits
SPE # N+178
SPE # N+179
DS3 Data
Bit Excluded Here
STS-1 SPE Data Stream
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| XRT75R12DIB-F | 功能描述:網(wǎng)絡(luò)控制器與處理器 IC 12 Channel 3.3V-5V temp -45 to 85C RoHS:否 制造商:Micrel 產(chǎn)品:Controller Area Network (CAN) 收發(fā)器數(shù)量: 數(shù)據(jù)速率: 電源電流（最大值）:595 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PBGA-400 封裝:Tray |
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