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XRT79L71
PRELIMINARY
589
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
STEP 1 - Make sure that the XRT79L71 is operating in the "Local-Timing" Mode.
Accomplish this by setting Bits 1 and 0 (TimRefSel[1:0]) within the "Framer Operating Mode" Register to some
value other than [0, 0].
STEP 2 - Configure the XRT79L71 to operate in the "Framer Loop-back" Mode
This is accomplished by setting Bit 7 (Framer Local Loop-back), within the "Framer Operating Mode" Register
to the value "1", as depicted below
7.2
USING THE PRBS PATTERN GENERATOR AND RECEIVER
The XRT79L71 contains a PRBS Pattern Generator and Receiver. The PRBS Pattern Generator resides
within the Transmit DS3/E3 Framer block and the PRBS Pattern Receiver resides within the Receive DS3/E3
Framer block.
If the PRBS Pattern Generator is enabled, then the XRT 79L71 will then ignore any data that is being applied to
the Transmit Payload Data Input Interface block. The payload bits (within each outbound DS3 or E3 frame) will
now be filled by the PRBS Pattern Generator block.
For DS3 Applications, the PRBS Pattern Generator will generate a 2^15-1 PRBS Pattern. As a consequence,
whenever the PRBS Pattern Generator has been enabled, then the Transmit DS3/E3 Framer block will
generate a DS3 signal that is of a "Framed" 2^15-1 PRBS Pattern.
For E3 Applications, the PRBS Pattern Generator will generate a 2^23-1 PRBS Pattern. As a consequence,
whenever the PRBS Pattern Generator has been enabled, then the Transmit DS3/E3 Framer block will
generate an E3 signal that is of a "Framed" 2^23-1 PRBS Pattern.
Similarly, if thePRBS Pattern Receiver is enabled, then it will do the following.
It will receive the payload DS3 or E3 data-stream from the Receive DS3/E3 Framer block
It will attempt to acquire "PRBS Lock" with this DS3 or E3 data-stream.
For DS3 Applications, the PRBS Pattern Receiver will be expecting a 2^15-1 PRBS Pattern within the data-
stream that it receives from the Receive DS3/E3 Framer block.
For E3 Applications, the PRBS Pattern
Receiver will be expecting a 2^23-1 PRBS Pattern within the data-stream that it receives from the Receive
DS3/E3 Framer block.
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framer
Local
Loop Back
IsDS3
Internal
LOS
Enable
RESET
Direct
Map
ATM
Frame
Format
TimRefSel[1:0]
R/W
0
1
0
1
0
X
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framer
Local
Loop Back
IsDS3
Internal
LOS
Enable
RESET
Direct
Map
ATM
Frame
Format
TimRefSel[1:0]
R/W
1
0
1
0
1
0
X