CN8380 Datasheet, PDF (63/91 Pages) Conexant Systems, Inc – integrated quad line interface unit unit for both 1.544 Mbps (T1) and 2.048 Mbps (E1) applications

CN8380
Quad T1/E1 Line Interface
3.0 Registers
3.3 Per Channel Registers
11, 21, 31, 41—Receiver Configuration (RLIU_CR)
7
6
UNIPOLAR
ZCS
5
CLK_POL
4
RAWMD
3
EQ_DIS
2
ATTN
R/W
1
0
—
SQUELCH
UNIPOLAR
ZCS
CLK_POL
RAWMD
EQ_DIS
ATTN
Unipolar Mode—Selects between unipolar and bipolar modes for digital transmit and receive
signals.
In unipolar mode, RPOSO/RNEGO signals are replaced by RDATO/BPV signals. AMI
encoded received data is decoded and output on RDATO in unipolar, NRZ format; and BPV
indicates that the currently received bit is a bipolar violation. TPOSI is replaced with TDATI
and accepts unipolar, NRZ formatted transmit data. TNEGI is not used in this mode. In
unipolar mode, ZCS can replace AMI encoding. Refer to the ZCS bit description below.
In bipolar mode, RPOSO/RNEGO signals output received data in bipolar dual-rail format,
where a high level on RPOSO indicates receipt of a positive AMI pulse, and a high level on
RNEGO indicates receipt of a negative AMI pulse on RTIP/RING inputs. TPOSI/TNEGI
inputs accept bipolar dual-rail transmit data, where a high on TPOSI causes a positive output
pulse on XTIP/XRING, and a high on TNEGI causes a negative output pulse.
0 = Digital transmit/receive signals are bipolar, dual-rail
1 = Digital transmit/receive signals are unipolar, NRZ
Zero Code Suppression Enable—Enables HDB3 or B8ZS zero code suppression
encoding/decoding on digital transmit and receive signals and is only applicable if unipolar
mode is selected. In T1 mode (T1/E1 = 1) [addr n0], B8ZS encoding/decoding is selected. In
E1 mode (T1/E1 = 0), HDB3 encoding/decoding is selected.
In the transmit direction, the ZCS encoder replaces sequences of eight or four 0s with a
recoverable code. In the receive direction, the ZCS decoder replaces received codes with eight
0s in T1 mode, or four 0s in E1 mode. The B8ZS code is 000VB0VB and the HDB3 code is
X00V; where B is a normal AMI pulse, V is a bipolar violation, and X is a “don't-care.” These
are standard T1 and E1 line code options.
0 = ZCS encode/decode disabled
1 = ZCS encode/decode enabled
Clock Polarity—Selects the digital receive data clocking edge. Normally, RPOSO/RNEGO is
output on the rising edge of RCKO. If CLK_POL is set to 1, RPOSO/RNEGO is output on the
falling edge of RCKO.
0 = Data out on rising RCKO
1 = Data out on falling RCKO
Raw Receive Mode—RPOSO/RNEGO data outputs are replaced by the data slicer output, and
RCKO is replaced by the logical OR of RPOSO/RNEGO. A high on RPOSO indicates a
positive pulse, and a high on RNEGO indicates a negative pulse on RTIP/RRING line inputs.
0 = Normal receiver output
1 = Slicer data output enabled
Equalizer Disable—Disables the receiver equalizer. (Test mode only)
0 = Equalizer enabled
1 = Equalizer disabled
Bridge Attenuation—Compensates for 20 dB resistive signal attenuation caused by placement
of bridge resistors in series with the normal receive termination resistance. Also, in this mode a
lower threshold for RALOS is selected to compensate for the 20 db attenuation.
0 = Normal receiver input levels
1 = 20 dB compensation enabled
N8380DSA
Conexant
3-11
4/21/99
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