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參數(shù)資料
| 型號(hào)： | XRT75R12DIB |
| 廠商： | EXAR CORP |
| 元件分類(lèi)： | 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(yè)數(shù)： | 99/131頁(yè) |
| 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
94
Figure 44 presents an alternative illustration of Telcordia GR-253-CORE’s recommendation on how to
asynchronously map DS3 data into an STS-1 SPE. In this case, the STS-1 SPE bit-format is expressed purely
in the form of "bit-types" and "numbers of bits within each of these types of bits". If one studies this figure
closely he/she will notice that this is the same "87 byte column x 9 row" structure that we have been talking
about when defining the STS-1 SPE. However, in this figure, the "user-data" field is now defined and is said to
consist of five (5) different types of bits. Each of these bit-types play a role when asynchronously mapping a
DS3 signal into an STS-1 SPE. Each of these types of bits are listed and described below.
Fixed Stuff Bits
Fixed Stuff bits are simply "space-filler" bits that simply occupy space within the STS-1 SPE. These bit-fields
have no functional role other than "space occupation". Telcordia GR-253-CORE does not define any particular
value that these bits should be set to. Each of the 9 rows, within the STS-1 SPE will contain 59 of these "fixed
stuff" bits.
DS3 Data Bits
The DS3 Data-Bits are (as its name implies) used to transport the DS3 data-bits within the STS-1 SPE. If the
STS-1 SPE is transporting a framed DS3 data-stream, then these DS3 Data bits will carry both the "DS3
payload data" and the "DS3 overhead bits". Each of the 9 rows, within the STS-1 SPE will contain 621 of these
"DS3 Data bits". This means that each STS-1 SPE contains 5,589 of these DS3 Data bit-fields.
Stuff Opportunity Bits
The "Stuff" Opportunity bits will function as either a "stuff" (or junk) bit, or it will carry a DS3 data-bit. The
decision as to whether to have a "Stuff Opportunity" bit transport a "DS3 data-bit" or a "stuff" bit depends upon
the "timing differences" between the DS3 data that is being mapped into the STS-1 SPE and the timing source
that is driving the STS-1 circuitry within the PTE.
As will be described later on, these "Stuff Opportunity" Bits play a very important role in "frequency-justifying"
the DS3 data that is being mapped into the STS-1 SPE. These "Stuff Opportunity" bits also play a critical role
in inducing Intrinsic Jitter and Wander within the DS3 signal (as it is de-mapped by the remote PTE).
Each of the 9 rows, within the STS-1 SPE consists of one (1) Stuff Opportunity bit. Hence, there are a total of
nine "Stuff Opportunity" bits within each STS-1 SPE.
Stuff Control/Indicator Bits
Each of the nine (9) rows within the STS-1 SPE contains five (5) Stuff Control/Indicator bits. The purpose of
these "Stuff Control/Indicator" bits is to indicate (to the de-mapping PTE) whether the "Stuff Opportunity" bits
(that resides in the same row) is a "Stuff" bit or is carrying a DS3 data bit.
If all five of these "Stuff Control/Indicator" bits, within a given row are set to "0", then this means that the
corresponding "Stuff Opportunity" bit (e.g., the "Stuff Opportunity" bit within the same row) is carrying a DS3
data bit.
Conversely, if all five of these "Stuff Control/Indicator" bits, within a given row are set to "1" then this means
that the corresponding "Stuff Opportunity" bit is carrying a "stuff" bit.
Overhead Communication Bits
Telcordia GR-253-CORE permits the user to use these two bits (for each row) as some sort of
"Communications" bit. Some Mapper devices, such as the XRT94L43 12-Channel DS3/E3/STS-1 to STS-12/
STM-1 Mapper and the XRT94L33 3-Channel DS3/E3/STS-1 to STS-3/STM-1 Mapper IC (both from Exar
Corporation) do permit the user to have access to these bit-fields.
However, in general, these particular bits can also be thought of as "Fixed Stuff" bits, that mostly have a "space
occupation" function.
8.2.2
DS3 Frequency Offsets and the Use of the "Stuff Opportunity" Bits
In order to fully convey the role that the "stuff-opportunity" bits play, when mapping DS3 data into SONET, we
will present a detailed discussion of each of the following "Mapping DS3 into STS-1" scenarios.
The Ideal Case (e.g., with no frequency offsets)
The 44.736Mbps + 1 ppm Case
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| XRT75R12 | TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR |
| XRT75R12IB | TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR |
| XRT75VL00 | E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR |
| XRT75VL00IV | E3/DS3/STS-1 LINE INTERFACE UNIT WITH JITTER ATTENUATOR |
| XRT79L71 | 1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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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 |
| XRT75R12DIB-L | 功能描述:LIN 收發(fā)器 Synch RoHS:否 制造商:NXP Semiconductors 工作電源電壓: 電源電流: 最大工作溫度: 封裝 / 箱體:SO-8 |
| XRT75R12ES | 功能描述:時(shí)鐘合成器/抖動(dòng)清除器 12CH T3/E3/STS1LIUJA 3.3V W/REDUNDANCY RoHS:否 制造商:Skyworks Solutions, Inc. 輸出端數(shù)量: 輸出電平: 最大輸出頻率: 輸入電平: 最大輸入頻率:6.1 GHz 電源電壓-最大:3.3 V 電源電壓-最小:2.7 V 封裝 / 箱體:TSSOP-28 封裝:Reel |
| XRT75R12IB | 功能描述:外圍驅(qū)動(dòng)器與原件 - PCI 12CH E3/DS3/STS W/JITTER R3 TECH RoHS:否 制造商:PLX Technology 工作電源電壓: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:FCBGA-1156 封裝:Tray |
| XRT75R12IB-F | 功能描述:外圍驅(qū)動(dòng)器與原件 - PCI 12 Channel 3.3V-5V temp -45 to 85C RoHS:否 制造商:PLX Technology 工作電源電壓: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:FCBGA-1156 封裝:Tray |
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