IDT82P2281
SINGLE T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
90
October 7, 2003
3.27.2
LOOPBACK
System Loopback, Payload Loopback, Local Digital Loopback 1 &
2, Remote Loopback and Analog Loopback are all supported in the
IDT82P2281. Their routes are shown in the Functional Block Diagram.
3.27.2.1
System Loopback
The System Loopback can only be implemented when the Receive
System Interface and the Transmit System Interface are in different
Non-multiplexed operating modes (one in Clock Master mode and the
other in Clock Slave mode). However, in T1/J1 mode, when either the
receive path or the transmit path is in T1/J1 mode E1 rate, the System
Loopback is not supported.
Distinguished by the loopback direction, the System Loopback can
be divided into System Remote Loopback and System Local Loopback.
When the data and signaling bits from the transmit path are looped to
the receive path, it is System Remote Loopback. When the data and sig-
naling bits from the receive path are looped to the transmit path, it is
System Local Loopback.
3.27.2.1.1
Enabled by the SRLP bit, the System Remote Loopback is imple-
mented. The data and signaling bits to be transmitted on the TSD and
TSIG pins are internally looped to the RSD and RSIG pins. When the
receive path is in Receive Clock Master mode and the transmit path is in
Transmit Clock Slave mode, the clock signal and the framing pulse from
the system side on the TSCK and TSFS pins are looped to the RSCK
and RSFS pins respectively. When the transmit path is in Transmit Clock
Master mode and the receive path is in Receive Clock Slave mode, the
clock signal and the framing pulse from the system side on the RSCK
and RSFS pins are looped to the TSCK and TSFS pins respectively.
In System Remote Loopback mode, the data stream to be transmit-
ted is still output to the line side, while the data stream received from the
line side is replaced by the System Remote Loopback data.
System Remote Loopback
3.27.2.1.2
Enabled by the SLLP bit, the System Local Loopback is imple-
mented. The received data and signaling bits to be output on the RSD
and RSIG pins are internally looped to the TSD and TSIG pins. When
the receive path is in Receive Clock Master mode and the transmit path
is in Transmit Clock Slave mode, the recovered clock signal and framing
pulse on the RSCK and RSFS pins are looped to the TSCK and TSFS
pins respectively. When the transmit path is in Transmit Clock Master
mode and the receive path is in Receive Clock Slave mode, the TSCK
and TSFS pins are looped to the RSCK and RSFS pins respectively.
In System Local Loopback mode, the data stream received from
the line side is still output to the system through the RSD and RSIG pins,
while the data stream to be transmitted through the TSD and TSIG pins
are replaced by the System Local Loopback data.
System Local Loopback