XR-T7296 Datasheet, PDF (6/16 Pages) Exar Corporation – DS3/STS-1, E3 Integrated Line Transmitter

XR-T7296
ABSOLUTE MAXIMUM RATINGS
Power Supply . . . . . . . . . . . . . . . . . . . . . . . -0.5 to +6.5V
Storage Temperature . . . . . . . . . . . . . . -65°C to 150°C
Voltage At Any Pin . . . . . . . . . . . . -0.5V to V_DD +0.5V
Power Dissipation SOJ Pkg. . . . . . . . . . . . . . . 725mW
Power Dissipation DIP Pkg. . . . . . . . . . . . . . . . . . . . 1W
Input Voltage (Any Pin) . . . . . . . . -0.5V to V_DD + 0.5V
Input Current (Any Pin) . . . . . . . . . . . . . . . . . . . . . 10mA
SYSTEM DESCRIPTION
B3ZS/HDB3 ENCODER
Data to be transmitted is input to the encoder block to be
encoded either in B3ZS or HDB3 as determined by the
state of the DS3,STS-1/E3 pin. Input data format can be
unipolar or binary. For binary signals, TPDATA and
TNDATA need to be connected together externally. The
line code used for DS3 is B3ZS. In this mode, each block
of three consecutive zeros is removed and replaced by
one of two codes which contain bipolar violation. These
replacement codes are B0V and 00V; where B indicates a
pulse conforming with the bipolar rule and V represents a
pulse violating the rule. The choice of these codes is
made such that an odd number of B pulses will be
transmitted between consecutive bipolar violation (V)
pulses. For E3 format, the line code is HDB3. The
encoding rule of HDB3 is similar to B3ZS except the
number of consecutive zeros is increased to four before a
code replacement can take place. The replacement
codes in this case are 000V and B00V.
STS-1 operation is achieved by placing the part in the
DS3 mode and using 51.84 MHz clocks. Logic operation
for STS-1 is the same for DS3.
TRANSMIT ALL ONE SELECT
Setting TAOS high causes continuous AMI encoded 1s to
be transmitted to the line. In this mode, input TPDATA and
TNDATA are ignored. If remote loop back (RLOOP) is set
high, any TAOS request is ignored.
REMOTE LOOP-BACK
Setting RLOOP high causes receive RPDATA and
RNDATA to be transmitted to the line through TTIP and
TRING. The data rate is determined by RCLK. In this
mode, TPDATA and TNDATA are ignored.
LOCAL LOOPBACK
Setting LLOOP high causes TPDATA and TNDATA to go
through both the encoder and the decoder. In this mode,
the transmit signal RCLKO, RPOS and RNEG
corresponds to TCLK, TPDATA and TNDATA
respectively. Unless overriden by TAOS request,
TPDATA and TNDATA will still be transmitted to the line.
Setting RLOOP and LLOOP high simultaneously is not
permitted.
B3ZS/HDB3 DECODER
The decoder block is included to perform B3ZS or HDB3
decoding as determined by the state of the DS3,
STS-1/E3 pin. In the B3ZS format, the decoder detects
both B0V and 00V pulses and replaces them with 000
data. If HDB3 decoding is selected by setting the DS3,
STS-1/E3 pin low, B00V and 000V pulses will be detected
and replaced with 0000 code. In both cases, bipolar
violation and coding errors which do not conform to the
coding scheme are detected and indicated at the BPV
output pin.
DECODER DISABLE
For testing purposes and in applications where the
decoder needs to be bypassed, the decoder can be
disabled by setting DECODIS high. In this mode all
bipolar violation pulses are indicated at the BPV pin.
BIPOLAR VIOLATION
The BPV pin will go high for one bit period when a bipolar
violation not corresponding to the appropriate coding rule
or a code error is detected on the RPDATA/RNDATA. The
violation pulse is always removed from the decoder
output RPOS / RNEG when DECODIS is set low.
Rev. 2.01
6