1.0 Product Description
1.3 Line Framing Functions
ATM Transmitter/Receiver with UTOPIA Interface
The CN8223 has a serial external framer interface for T1, E1, T3, and E3. The
internal B3ZS/HDB3 encoder/decoder can be bypassed in any mode for direct
input/output of NRZ data and clock.
The line signal interface consists of clock, serial or octet data, and sync
signals from either the internal or external framers. Both framed and unframed
modes are usable at DS1, E1, DS3, and E3 line rates. In framed mode, the
frame/overhead bit positions of the transmission format are located through a
synchronization signal and are generated as idle bits or ignored. In unframed
mode, a serial signal that contains no line overhead bit positions is expected.
The transmitter interface has a clock signal input and provides a serial or octet
data output. The receive signal interface consists of input clock and serial or octet
data from the transmission physical layer framer. Also, synchronization inputs are
provided for use with external framers. The transmit and receive sections of the
interface are clocked independently.
A parallel line interface is available for external framers and other devices. It
consists of a receive clock and octet and a transmit clock and octet. This interface
permits clocking externally recovered octets directly to and from the cell
delineation function block. Use of the parallel interface assumes all line overhead
information has been removed externally and proper octet alignment has been
1.3.2 Line Loopback
A line loopback connects the receive clock and data inputs directly to the transmit
clock and data outputs. LCVs are preserved in this loopback. Raw yellow alarm
indications and Out-of-Frame (OOF) events are integrated to provide yellow
alarm and Loss-of-Frame (LOF) indications, respectively. PHY error counters can
be programmed to accumulate errors over one-second periods and latch the
results. Line framing functions are described in detail in Section 2.2.