INTRODUCTION
DOCUMENT SCOPE
This document describes the function and operation of the 83C694D Twisted-Pair Interface and Manchester Encoder/Decoder. It includes a description of external logic necessary for the efficient use of this device and its proper role in the chip set which includes the 83C690 and 83B692 as shown in Figure 1-1. Figure 1-2 provides a functional block diagram of the 83C694D chip itself.

GENERAL DESCRIPTION
The 83C694D is used for applications where Twisted-Pair Interface (TPI) and/or Attachment Unit Interface (AUI) functions are required. Its two main functions are to:

1. Receive a digital data stream from a low-level input signal and
2. Convert a digital output data stream into an analog high-current signal for transmission across a network cable.

This means that the 83C694D serves as the logical link between a network cable on one end and a digital controller chip (such as the 83C690) on the other end.

FEATURES
Features of the 83C694D include:
• Twisted-Pair interface solution for IEEE 802.3 10BaseT Standard
• Compatible with Ethernet II (10BASE5) and Cheapernet (10BASE2) IEEE 802.3 Standards
• Smart Squelch© digital noise filter at receive and collision inputs to reject noise and digital noise on twisted-pair receive inputs.
• Direct connection to the transceiver (AUI) cable
• 16V fault protection at the AUI transmitter interface
• 10 Mbps Manchester encoding/ decoding with receive clock recovery
• Low power, 1.25µ CMOS technology
• TTL/MOS-compatible controller interface
• Externally-selectable half- or full-step modes of operation at AUI TX± outputs
• Loopback capability for diagnostics
• Single station interface operation
• Link test generation and digital equalization for twisted-pair transmitter
• Automatic phase detection
• AUI/TP autoselect
• Built-in LED drivers for transmit, receive, link test and polarity status indicators