cx29503 Mindspeed Technologies, cx29503 Datasheet - Page 120

• Manufacturer Part Number: cx29503
• Description: Cx29503 Broadband Access Multiplexer Data Sheet
• Manufacturer: Mindspeed Technologies

Loopbacks
5-2
Type 4 Loopback (DS2-Activated DS1 Line Loopback)—The DS2-C bit stream is
examined for a DS1 loopback sequence. The software is capable of enabling/
disabling this feature and optionally inserting AISs to downstream components. If
this feature is enabled by the software, the hardware will autonomously enable
loopback when a loopback command is received.
If the software has requested AIS insertion, the hardware will insert an AIS to
downstream components for the duration of the loopback. The hardware will
indicate, via a status bit, that a loopback is in process. The hardware will
autonomously terminate the loopback after receiving the appropriate command in
the C-bit stream and update the status register. The software is capable of inserting
this DS1 loopback code into transmitted DS2 overhead bits.
Type 5 Loopback (DS3 Source Loopback)—DS3 TX-to-RX loopback is
implemented. This loopback feature is activated/deactivated under software
control. The transmitted signal stream is fed into the receive path. DS3 input
signals at the RPOS and RNEG pins are ignored. The Receive clock is substituted
by the Transmit clock. The software may choose to issue an AIS or LOS indication
on the DS3 transmit pins, TPOS and TNEG.
Type 6 Loopback (DS3 Shallow Line Loopback)—The DS3 RX-to-TX loopback is
implemented. This loopback feature is activated/deactivated under software
control. The received signal is echoed on the transmit pins TPOS and TNEG. The
Transmit clock is substituted with the Receive clock. Signals on RNEG and RPOS
are fed to the DS3 framer. The software will have the option of inserting an AIS at
the DS3 framer output instead of demultiplexed signals.
Type 8 Loopback (DS3 Remote Line Loopback)—The DS3 remote line loopback
is implemented. This loopback feature is activated/deactivated under software
control. The received signal after B3ZS/HDB3 decoding is looped back to the
transmitter B3ZS/HDB3 encoder.
Mindspeed Technologies™
Preliminary Information
CX29503 Data Sheet
29503-DSH-002-B