Am79C981

The Integrated Multiport Repeater Plus (IMR+) chip is a VLSI circuit that provides a system-level solution to designing
a compliant 802.3 repeater incorporating 10BASE-T transceivers. The device integrates the Repeater functions specified by Section 9 of the IEEE 802.3 standard and Twisted-Pair Transceiver functions complying with the 10BASE-T standard. The Am79C981 provides eight integral twisted-pair medium attachment units (MAUs) and an attachment unit interface (AUI) port in an 84-pin plastic leaded chip carrier (PLCC).

A network based on the Am79C981 standard uses unshielded twisted-pair cables, thereby providing an economical
solution to networking by allowing the use of low-cost unshielded twisted-pair (UTP) cable or existing telephone wiring.

The total number of ports per repeater unit can be increased by connecting multiple IMR+ devices through their expansion ports, minimizing the total cost per repeater port. Furthermore, a general-purpose attachment unit  nterface (AUI) provides connection capability to 10BASE-5 (Ethernet) and 10BASE-2 (Cheapernet) coaxial networks, as well as 10BASE-F and/or Fiber Optic Inter-Repeater Link (FOIRL) fiber segments. Network management and test functions are provided through TTL-compatible I/O pins.

The IMR+ Am79C981 interfaces directly with AMD's Am79C987 Hardware Implemented Management Information Base™ (HIMIB) chip to build a fully managed multiport repeater as specified by the IEEE 802.3 (Layer Management for 10 Mb/s Baseband Repeaters) standard. When the IMR+ and HIMIB devices are interconnected, complete repeater and per-port statistics are maintained and can be accessed on demand using a simple 8-bit parallel interface.