![](http://datasheet.mmic.net.cn/330000/PM4351_datasheet_16444271/PM4351_441.png)
STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
PROPRIETARY AND CONFIDENTIAL
417
Pattern Type
PT
PL
PI#1
PI#2
PI#3
PI#4
TINV
RINV
1 in 4
Inband loopback
activate
Inband loopback
deactivate
00
00
03
04
F1
F0
FF
FF
FF
FF
FF
FF
0
0
0
0
00
02
FC
FF
FF
FF
0
0
Notes for the Pseudo Random and Repetitive Pattern Generation Tables
1. The PS bit and the QRSS bit are contained in the PRGD Control register
2. PT = Tap Register
3. PL = Shift Register Length Register
4. PI#1 = PRGD Pattern Insertion #1 Register
5. PI#2 = PRGD Pattern Insertion #2 Register
6. PI#3 = PRGD Pattern Insertion #3 Register
7. PI#4 = PRGD Pattern Insertion #4 Register
8. The TINV bit and the RINV bit are contained in the PRGD Control register
14.8 Using the Loopback Modes
The COMET provides four loopback modes to aid in network and system
diagnostics. The network loopbacks (Payload and Line) can be initiated at any
time via the μP interface, but are usually initiated once an inband loopback
activate code is detected. The system Diagnostic Digital loopback can be
initiated at any time by the system via the μP interface to check the path of
system data through the framer. The Per-DS0 loopback permits the payload to
be looped-back on a per-DS0 basis to allow network testing without taking an
entire link off-line.
14.8.1 Line Loopback
When LINE loopback (LINELB) is initiated by setting the LINELB bit in the
Master Diagnostics Register (00AH) to logic 1, the COMET is configured to
internally connect the recovered data to the transmit jitter attenuator, TJAT. In
analog mode (RUNI is logic 0), the data sent to the TJAT is the recovered data