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参数资料
| 型号： | CS62180 |
| 厂商： | Cirrus Logic, Inc. |
| 元件分类： | 通信及网络 |
| 英文描述： | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| 中文描述： | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| 文件页数： | 48/50页 |
| 文件大小： | 411K |
| 代理商： | CS62180 |
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Alarms
Figure A10 shows a useful overview of the alarm
operation in a PCM link. When an intermediate
monitoring system (or central office repeater) de-
tects a loss of signal, it transmits an all "1’s"
signal (Blue alarm, or Alarm Indication Signal)
on the line to maintain clock recovery operation
in the subsequent digital repeaters and the desti-
nation’s receiver. The same Blue alarm may be
used by the source transmitter if, for some rea-
son, it cannot maintain normal functionality
(such as during loopback).
When the loss of signal is detected at the inter-
mediate monitor, an internal Red alarm (also
known as a Service Alarm Indication, or Prompt
Maintenance Alarm) is generated. While in a
Red alarm mode, the monitor transmits a Yellow
alarm back to the source’s receiver, indicating a
remote loss of alignment. This Yellow alarm in-
forms the source that there’s a problem farther
down the line and it’s transmission is not being
received at the destination.
Zero Substitution
As was mentioned in the T1 overview, data is
transmitted over dual twisted-pair cable with
digital repeaters at 6000 ft. intervals. It is en-
coded in a bipolar AMI (Alternate Mark
Inversion) format. Successive "1’s" are encoded
alternately as positive and negative voltage
pulses. A zero is simply an absence of pulses.
This means that a long stream of "0’s" is indis-
tinguishable from a dead line. Clock recovery
circuits in the network maintain clock synchroni-
zation by syncing to the "1’s" pulses in the
transmission stream. Synchronization may be
lost if there are too many consecutive zero’s,
hence there is a general requirement that there be
at least 12.5 % "1’s" density in the transmission
stream. Furthermore, no more than 15 consecu-
tive "0’s" are allowable. Various zero substitution
schemes have been developed to meet these re-
quirements. The CS62180B
supports B7
and B8ZS zero suppression formats.
B7 Zero Substitution
B7 zero substitution guarantees at least one "1"
in all DS0 channels. This satasfies the 12.5 %
ones density, and guarantees that more than 15
consecutive zeros will never occur. In B7 substi-
tution systems, the 7
th
bit (2
nd
LSB) of an all
zero channel is forced to a "1". This strategy
maintains 1’s density in voice grade transmis-
sion, with negligible audible interference. The
drawback with the B7 format is that it’s impossi-
ble for the receiving end to detect and remove
the changed bits. This makes B7 zero suppres-
sion unacceptable for clear channel transmission,
in which the integrity of the data must be main-
tained.
B8ZS Zero Substitution
B8ZS (Bipolar Eight Zero Substitution) satisfies
the one’s density requirement without corrupting
transmission data. Instead of operating on indi-
vidual channels, the B8ZS format looks at the
entire transmission stream. Any eight consecutive
zeros are replaced with an 8 bit code. This code
uses specific bipolar violations of the AMI for-
mat to distinguish it from the ordinary data. If
the last "1" transmitted before a string of zeros
was encoded as a positive pulse, then the B8ZS
code for the next eight bits will be 000+-0-+.
Similarly, if the last "1" was a negative pulse,
then the code will be 000-+0+-. In either case,
bipolar violations occur in the fourth and seventh
bits. These violations are decoded as a string of
Blue Alarm
Monitor
Loss of
Signal = Red
Alarm
Yellow Alarm
Source
Transmit
Receive
Transmit
Receive
Destination
Digital
Repeater
Yellow
Alarm
Yellow
Alarm
Blue
Alarm
Figure A10. Alarm Operation on a T1 Link.
CS62180B
48
DS225PP
2
相关PDF资料 |
PDF描述 |
|---|---|
| CS62180B | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| CS62180B-IL | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| CS62LS4008GC | Low Power CMOS SRAM 512K X 8 Bits |
| CS62LS4008GI | Low Power CMOS SRAM 512K X 8 Bits |
| CS62LS4008HC | Low Power CMOS SRAM 512K X 8 Bits |
相关代理商/技术参数 |
参数描述 |
|---|---|
| CS62180A | 制造商:未知厂家 制造商全称:未知厂家 功能描述:T1 Framer |
| CS62180A-IL | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Framer/Formatter |
| CS62180A-IP | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Framer/Formatter |
| CS62180B | 制造商:CIRRUS 制造商全称:Cirrus Logic 功能描述:T1 FRAMER |
| CS62180B-IL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Cirrus Logic 功能描述: |
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