XRT73LC00A_08 Datasheet, PDF (28/63 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT

REV. 1.0.1
XRT73LC00A
E3/DS3/STS-1 LINE INTERFACE UNIT
TABLE 3: SELECTING THE DATA RATE FOR THE
XRT73LC00A VIA THE STS-1/DS3 AND THE E3 BIT-
FIELDS WITHIN COMMAND REGISTER CR4 (HOST
MODE)
SELECTED DATA RATE
STS-1/DS3
E3
E3
Don't Care
1
DS3
0
0
STS-1
1
0
The results of making these selections are:
1. The VCO Center Frequency of the Clock Recovery Phase-Locked-Loop is configured to match the
selected data rate.
2. The B3ZS/HDB3 Encoder and Decoder blocks are configured to support B3ZS Encoding/Decoding if the
DS3 or STS-1 data rates were selected or,
3. The B3ZS/HDB3 Encoder and Decoder blocks are configured to support HDB3 Encoding/Decoding if the
E3 data rate was selected.
4. The on-chip Pulse-Shaping circuitry is configured to generate Transmit Output pulses of the correct shape
and width to meet the applicable pulse template requirement.
5. The LOS Declaration/Clearance Criteria is established.
2.0 THE TRANSMIT SECTION
Figure 1 indicates that the Transmit Section of the XRT73LC00A consists of the following blocks:
• Transmit Logic Block
• Duty Cycle Adjust Block
• HDB3/B3ZS Encoder
• Pulse Shaping Block
The purpose of the Transmit Section in the XRT73LC00A is to take TTL/CMOS level data from the terminal
equipment and encode it into a format that can:
1. be efficiently transmitted over coaxial cable at E3, DS3 or STS-1 data rates.
2. be reliably received by the Remote Terminal at the other end of the E3, DS3 or STS-1 data link.
3. comply with the applicable pulse template requirements.
2.1 The Transmit Logic Block
The purpose of the Transmit Logic Block is to accept either Dual-Rail or Single-Rail (a binary data stream) TTL/
CMOS level data and timing information from the Terminal Equipment.
Accepting Dual-Rail Data from the Terminal Equipment
The XRT73LC00A accepts Dual-Rail data from the Terminal Equipment via the following input signals:
• TPDATA
• TNDATA
• TCLK
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