
XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
216
7.1.2
Detailed Functional Description of the
Receive DS3 Framer
7.1.2.1
Receiving and Decoding Incoming
DS3 Data—via DS3 Line
The Receive DS3 Framer will receive timing and data
information from the incoming DS3 data stream.
The DS3 Timing information will be received via the
RxLineClk input pin; and the DS3 data information
will be received via the RxPOS and RxNEG input pins.
The Receive DS3 Framer is capable of receiving DS3
data pulses in unipolar or bipolar format. If the
Receive DS3 framer is operating in the bipolar for-
mat, then it can be configured to decode either AMI
or B3ZS line code data. Each of these input formats
and line codes will be discussed in detail, below.
7.1.2.1.1
If the Receive DS3 Framer is operating in the Unipolar
mode, then it will receive the Single Rail NRZ DS3
data pulses via the RxPOS input pin. The Receive
DS3 Framer will also receive its timing signal via the
RxLineClk signal. No data pulses will be applied to
the RxNEG input pin. The Receive DS3 Framer
receives a logic “1” when a logic “1” level signal is
present at the RxPOS pin, during the sampling edge
of the RxLineClk signal. Likewise, a logic “0” is
received when a logic “0” level signal is applied to the
RxPOS pin. Figure 62 presents an illustration of the
behavior of the RxPOS, RxNEG and RxLineClk pins
when the UNI is operating in the Unipolar mode.
Unipolar Coding
F
IGURE
61. F
UNCTIONAL
B
LOCK
D
IAGRAM
OF
R
ECEIVER
F
RAMER
Over Head
Processor
Frame Synchronizer
B3ZS
Decoder
Serial/Nibble
Converter
PayLoad
Overhead
MUX
Line Detector
ExtLOS
LOS Interrupt
AIS Interrupt
Idle Interrupt
RxAIS
RxLOS
RxIdle
RxPOS
RxNEG
RxLineClk
RxInFrame
RxFrame
RxOHFrame
RxOHClk
SubFrame
Counter
(Divide by 4)
Nibble
Counter
(Divide by 4)
Packet
Counter
(Divide by 85)
Frame
Counter
(Divide by 7)
Justify
RxFrame
OR
Gate
LCV Error
(to PMON)
RxNBClk
RxNBData
RxOFF
RxOOF
RxNBDat[4]
RxNBClk
New Frame
Alignment
Interrupt
To
Int
Block
Timing & Control
RxLineClk
PayLoad
Data
Enable
Enable
Interrupt from OH
Processor
RxOHFrame
RxOHClk
RxOH
RxFEBE
RxFrame
(To Tx
Framer)