參數(shù)資料
型號: XRT73L04
廠商: Exar Corporation
英文描述: 4 Channel E3/DS3/STS-1 Line Interface Unit(4通道 E3/DS3/STS-1線接口單元)
中文描述: 4頻道E3/DS3/STS-1線路接口單元(4通道E3/DS3/STS-1線接口單元)
文件頁數(shù): 32/62頁
文件大?。?/td> 781K
代理商: XRT73L04
XRT73L04
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. P1.0.5
á
PRELIMINARY
28
ates pulses of the appropriate shapes and width to
meet the applicable pulse template requirements.
The widths of these output pulses are defined by the
width of the half-period pulses within the TxClk(n) sig-
nal.
However, if the widths of the pulses within the Tx-
Clk(n) clock signal are allowed to vary significantly,
this could jeopardize the chip's ability to generate
Transmit Output pulses of the appropriate width and
thereby not meet the Pulse Template requirement
specification. Consequently, the chip's ability to gen-
erate compliant pulses could depend upon the duty
cycle of the clock signal applied to the TxClk(n) input
pin.
The Transmit Clock Duty Cycle Adjust Circuitry ac-
cepts clock pulses via the TxClk(n) input pin at duty
cycles ranging from 30% to 70% and converts them
to a 50% duty cycle.
2.3
T
HE
HDB3/B3ZS E
NCODER
B
LOCK
The purpose of the HDB3/B3ZS Encoder Block is to
aid in the Clock Recovery process at the Remote Ter-
minal Equipment by ensuring an upper limit on the
number of consecutive zeros that can exist within the
line signal.
2.3.1
B3ZS Encoding
If the XRT73L04 has been configured to operate in
the DS3 or SONET STS-1 Modes, then the HDB3/
B3ZS Encoder blocks operate in the B3ZS Mode.
When the Encoder is operating in this mode, it pars-
es through and searches the Transmit Binary Data
Stream from the Transmit Logic Block for the occur-
rence of three (3) consecutive zeros (e.g., "000"). If
the B3ZS Encoder finds an occurrence of three con-
secutive zeros, then it substitutes these three "0’s",
with either a "00V" or a "B0V" pattern.
Where:
"B" represents a Bipolar pulse that is compliant with
the Alternating Polarity requirements of the AMI (Al-
ternate Mark Inversion) line code; and
"V" represents a Bipolar Violation (e.g., a bipolar
pulse that violates the Alternating Polarity require-
ments of the AMI line code).
The B3ZS Encoder decides whether to substitute
with either the “00V" or the "B0V" pattern in order to
insure that an odd number of bipolar pulses exist be-
tween any two consecutive violation pulses.
Figure 14 illustrates the B3ZS Encoder at work with
two separate strings of three (or more) consecutive
zeros
2.3.2
If the XRT73L04 is configured to operate in the E3
Mode, then the HDB3/B3ZS Encoder blocks operate
in the HDB3 Mode. When the Encoder is operating in
this mode, it parses through and searches the Trans-
mit Data Stream from the Transmit Logic Block for the
occurrence of four (4) consecutive zeros (e.g.,
"0000"). If the HDB3 Encoder finds an occurrence of
four consecutive zeros, then it substitutes these four
HDB3 Encoding
"0’s", with either a "000V" or a "B00V" pattern. The
HDB3 Encoder decides whether to substitute with ei-
ther the "000V" or the "B00V" pattern in order to in-
sure that an odd number of bipolar pulses exist be-
tween any two consecutive violation pulses.
Figure 15illustrates the HDB3 Encoder at work with
two separate strings of four (or more) consecutive ze-
ros.
F
IGURE
14. A
N
E
XAMPLE
OF
B3ZS E
NCODING
1
1
1
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
B
0
V
0
0
V
Line Signal
TxClk
TNData
TPData
Data
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參數(shù)描述
XRT73L04A 制造商:EXAR 制造商全稱:EXAR 功能描述:4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
XRT73L04AIV 制造商:EXAR 制造商全稱:EXAR 功能描述:4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
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