XRT91L30ES Exar, XRT91L30ES Datasheet - Page 33

• Manufacturer Part Number: XRT91L30ES
• Description: Bus Transceivers
• Manufacturer: Exar

Specifications of XRT91L30ES

• Product Category: Bus Transceivers
• Rohs: yes

REV. 1.0.2
Analog Local Loopback (ALOOP) controls a more comprehensive version of digital local loopback in which the
point where the transmit data is looped back is moved all the way back to the high-speed receive I/O. The
transmit data from the transmit parallel interface TXDI[7:0] is serialized and presented to the high-speed
transmit output TXOP/N using the high-speed 622.08/155.52 MHz transmit clock generated from the clock
multiplier unit. In addition, the high-speed transmit data TXOP/N is looped back to the receive clock and data
recovery unit, replacing the RXIP/N. The signal is then processed by the CDR, and is sent through the serial to
parallel converter and presented at the low-speed receive parallel interface RXDO[7:0]. ALOOP is invoked by
asserting the ALOOP pin "High." A simplified block diagram of parallel remote loopback is shown in
Receive Data mute upon LOS, as shown in
F
The serial remote loopback and the digital local loopback can be combined to form a split loopback. The
output of the parallel to serial converter is looped back and presented to the high-speed input of the receiver
serial to parallel converter. The high-speed serial receive data from RXIP/N is presented at the high speed
transmit output TXOP/N, and the high-speed recovered clock is selected to re-time the high speed transmit
data output. A simplified block diagram of parallel remote loopback is shown in
F
4.3
4.4
IGURE
IGURE
20. A
21. S
Analog Local Loopback
Split Loopback
Rx Parallel Output
Rx Parallel Output
Tx Parallel Input
Tx Parallel Input
PLIT
NALOG
L
OOPBACK
L
OCAL
L
OOPBACK
SIPO
PISO
Analog Local Loop back
Split Loopback
PISO
SIPO
CDR
Figure
STS-12/STM-4 OR STS-3/STM-1 SONET/SDH TRANSCEIVER
Re-Timer
7, applies to Analog Local Loopback.
Input Drivers
29
LVPECL
Re-Timer
CDR
Output Drivers
Output Drivers
Input Drivers
LVPECL
LVPECL
LVPECL
Figure
21.
Tx Serial Output
Tx Serial Output
Rx Serial Input
XRT91L30
Figure
20.