![](http://datasheet.mmic.net.cn/IDT--Integrated-Device-Technology-Inc/IDT82V2088DRG_datasheet_97517/IDT82V2088DRG_28.png)
28
INDUSTRIAL
TEMPERATURE RANGES
OCTAL CHANNEL T1/E1/J1 LONG HAUL/SHORT HAUL LINE INTERFACE UNIT
3.6
TRANSMIT AND DETECT INTERNAL PATTERNS
The internal patterns (All Ones, All Zeros, PRBS/QRSS pattern and
Activate/Deactivate Loopback Code) will be generated and detected by the
IDT82V2088. TCLKn is used as the reference clock by default. MCLK can
also be used as the reference clock by setting the PATT_CLK bit (MAINT0,
0AH...) to ‘1’.
If the PATT_CLK bit (MAINT0, 0AH...) is set to ‘0’ and the PATT[1:0] bits
(MAINT0, 0AH...) are set to ‘00’, the transmit path will operate in normal
mode.
3.6.1
TRANSMIT ALL ONES
In transmit direction, the All Ones data can be inserted into the data
stream when the PATT[1:0] bits (MAINT0, 0AH...) are set to ‘01’. The trans-
mit data stream is output from TTIPn/TRINGn. In this case, either TCLKn
or MCLK can be used as the transmit clock, as selected by the PATT_CLK
bit (MAINT0, 0AH...).
3.6.2
TRANSMIT ALL ZEROS
If the PATT_CLK bit (MAINT0, 0AH...) is set to ‘1’, the All Zeros will be
inserted into the transmit data stream when the PATT[1:0] bits (MAINT0,
0AH...) are set to ‘00’.
3.6.3
PRBS/QRSS GENERATION AND DETECTION
A PRBS/QRSS will be generated in the transmit direction and detected
in the receive direction by IDT82V2088. The QRSS is 220-1 for T1/J1 appli-
cations and the PRBS is 215-1 for E1 applications, with maximum zero
restrictions according to the AT&T TR62411 and ITU-T O.151.
When the PATT[1:0] bits (MAINT0, 0AH...) are set to ‘10’, the PRBS/
QRSS pattern will be inserted into the transmit data stream with the MSB
first. The PRBS/QRSS pattern will be transmitted directly or invertedly.
The PRBS/QRSS in the received data stream will be monitored. If the
PRBS/QRSS has reached synchronization status, the PRBS_S bit
(STAT0, 14H...) will be set to ‘1’, even in the presence of a logic error rate
less than or equal to 10-1. The criteria for setting/clearing the PRBS_S bit
PRBS data canbe inverted throughsetting the PRBS_INVbit(MAINT0,
0AH...).
Any change of PRBS_S bit will be captured by PRBS_IS bit (INTS0,
16H...). The PRBS_IES bit (INTES, 13H...) can be used to determine
whetherthe ‘0’ to‘1’changeof PRBS_Sbitwill becapturedby thePRBS_IS
bitoranychangesofPRBS_SbitwillbecapturedbythePRBS_ISbit.When
the PRBS_IS bit is ‘1’, an interrupt will be generated if the PRBS_IM bit
(INTM0, 11H...) is set to ‘1’.
The received PRBS/QRSS logic errors can be counted in a 16-bit
counter if the ERR_SEL [1:0] bits (MAINT6, 10H...) are set to ‘00’. Refer to
operation of the error counter.
3.7
LOOPBACK
To facilitate testing and diagnosis, the IDT82V2088 provides four dif-
ferent loopback configurations: Analog Loopback, Digital Loopback,
Remote Loopback and Inband Loopback.
3.7.1
ANALOG LOOPBACK
WhentheALPbit(MAINT1,0BH...)issetto‘1’,thecorrespondingchan-
nel is configured in Analog Loopback mode. In this mode, the transmit sig-
nals are looped back to the Receiver Internal Termination in the receive
path then output from RCLKn, RDn, RDPn/RDNn. At the same time, the
transmit signals are still output to TTIPn/TRINGn in transmit direction.
Fig-3.7.2
DIGITAL LOOPBACK
WhentheDLPbit(MAINT1,0BH...)issetto‘1’,thecorrespondingchan-
nel is configured in Digital Loopback mode. In this mode, the transmit sig-
nals are looped back to the jitter attenuator (if enabled) and decoder in
receive path, then output from RCLKn, RDn, RDPn/RDNn. At the same
time, the transmit signals are still output to TTIPn/TRINGn in transmit direc-
Both Analog Loopback mode and Digital Loopback mode allow the
sending of the internal patterns (All Ones, All Zeros, PRBS, etc.) which will
overwrite the transmit signals. In this case, either TCLKn or MCLK can be
used as the reference clock for internal patterns transmission.
3.7.3
REMOTE LOOPBACK
WhentheRLPbit(MAINT1,0BH...)issetto‘1’,thecorrespondingchan-
nel is configured in Remote Loopback mode. In this mode, the recovered
clock and data output from Clock and Data Recovery on the receive path
is looped back to the jitter attenuator (if enabled) and Waveform Shaper in
Table-20 Criteria for Setting/Clearing the PRBS_S Bit
PRBS/QRSS
Detection
6 or less than 6 bit errors detected in a 64 bits hopping window.
PRBS/QRSS
Missing
More than 6 bit errors detected in a 64 bits hopping window.