NE8392C

The NE8392C Coaxial Transceiver Interface (CTI) is a bipolar coaxial line driver/receiver for Ethernet (10base5) and Thin Ethernet (10base2) local area networks. The CTI NE8392C is connected between the coaxial cable and the Data Terminal Equipment (DTE) and consists of a receiver, transmitter, receive-mode collision detector, heartbeat generator and jabber timer (see Block Diagram). The transmitter output connects directly to a doubly terminated 50W cable, while the receiver output, collision detector output and transmitter input are connected to the DTE through isolation transformers. Isolation between the CTI and the DTE is an IEEE 802.3 requirement, NE8392C can be met on signal lines by using a set of pulse transformers normally available in a standard 16-pin DIP. Power isolation for the

CTI NE8392C is achieved using DC-to-DC conversion through a power transformer (see Figure 1, Connection Diagram). During transmission the jabber timer is initiated to disable the CTI transmitter in the event of a longer than legal length data packet. Receive-mode collision detection circuitry monitors the signals on the coaxial cable to determine the presence of colliding packets and signals the DTE in the event of a collision. At the end of every transmission the heartbeat generator creates a pseudo collision for a short time to ensure that the collision circuitry is functioning correctly. The heartbeat function can be disabled for repeater applications.

The CTI NE8392C is normally part of a three chip set that implements a complete Ethernet/ Thin Ethernet network interface for a DTE (see Figure 2, Interface Diagram). The other chips are a Serial Network Interface (SNI) and a Network Interface Controller (NIC). The SNI NE8392C provides Manchester Encoding and Decoding while the NIC handles the media access protocol and buffer management tasks.