CN8380 Datasheet, PDF (32/91 Pages) Conexant Systems, Inc – integrated quad line interface unit unit for both 1.544 Mbps (T1) and 2.048 Mbps (E1) applications

2.0 Circuit Description
2.4 Transmitter
CN8380
Quad T1/E1 Line Interface
2.4 Transmitter
Bipolar or unipolar, NRZ digital transmit data are input on TPOSI and TNEGI
using the transmit clock TCLK. Data are converted into AMI pulses, shaped
according to required standards, and transmitted to the line. Figure 2-5 illustrates
the relationship between the AMI transmitted signal, the transmit clock, and the
data inputs. This section discusses each transmitter block, from the digital inputs
to the line output.
Figure 2-5. Transmitter Signals
TCLK
TPOSI
(Bipolar)
TNEGI
(Bipolar)
TDATI
(Unipolar)
XTIP,
XRING
8380_010
1
1
0
1
1
0
0
1
Throughput
Delay
2.4.1 Transmit Digital Interface
2.4.1.1 Bipolar Mode
The digital transmitter inputs, TPOSI[n] and TNEGI[n], accept bipolar or
unipolar NRZ formatted data for transmission and are sampled by the falling edge
of TCLK[n], where [n] is channel number 1 to 4. TCLK[n] is the line rate
transmit clock and is normally supplied externally from a line rate source, but can
also be sourced internally (only in Host Mode) from the CLAD. If sourced
internally, TCLK[n] is configured as an output to provide the line rate clock to
external circuitry. TCLK[n] direction is configured globally for all channels by
writing to register bit TCLK_I/O [GCR; addr 01].
In bipolar mode, TPOSI/TNEGI inputs accept bipolar dual-rail transmit data
where a high on TPOSI causes a positive output pulse and a high on TNEGI
causes a negative output pulse on XTIP/XRING. In this mode, the TZCS encoder
is not available. In Hardware Mode, bipolar operation is enabled globally for all
channels by pulling the UNIPOLAR pin low. In Host Mode, bipolar operation is
2-10
Conexant
N8380DSA
Advance Information