Am79C961A

The PCnet-ISA II controller, a single-chip Ethernet controller, is a highly integrated system solution for the PC-AT Industry Standard Architecture (ISA) architecture. It is designed to provide flexibility and compatibility with any existing PC application. This highly integrated 132-pin VLSI Am79C961A is specifically designed to reduce parts count and cost, and addresses applications where higher system throughput is desired. The PCnet-ISA II controller is fabricated with AMD's advanced low-power CMOS process to provide low standby current for power sensitive applications.

The Am79C961A can be configured into one of three different architecture modes to suit a particular PC application. In the Bus Master mode, all transfers are performed using the integrated DMA controller. This configuration enhances system performance by allowing the PCnet-ISA II controller to bypass the platform DMA controller and directly address the full 24-bit memory space. The implementation of Bus Master mode allows minimum parts count for the majority of PC applications. The PCnet-ISA II can also be configured as a Bus Slave with either a Shared Memory or Programmed I/O architecture for compatibility with low-end machines, such as PC/XTs that do not support Bus Masters, and high-end machines that require local packet buffering for increased system latency.

The Am79C961A is designed to directly interface with the ISA or EISA system bus. It contains an ISA Plug and Play bus interface unit, DMA Buffer Management Unit, 802.3 Media Access Control function, individual 136-byte transmit and 128-byte receive FIFOs, IEEE 802.3 defined Attachment Unit Interface (AUI), and a Twisted Pair Transceiver Media Attachment Unit. Full duplex network operation can be enabled on any of the device's network ports. The PCnet-ISA II controller is also register compatible with the LANCE (Am7990) Ethernet controller and PCnet-ISA. The DMA Buffer Management Unit supports the LANCE descriptor software model. External remote boot and Ethernet physical address PROMs and Electrically Erasable Proms are also supported.

This advanced Am79C961A has the built-in capability of automatically selecting either the AUI port or the Twisted Pair transceiver. Only one interface is active at any one time. The individual 136-byte transmit and 128-byte receive FIFOs optimize system overhead, providing sufficient latency during packet transmission and reception, and minimizing intervention during normal network error recovery. The integrated Manchester encoder/decoder eliminates the need for an external Serial Interface Adapter (SIA) in the node system. If support for an external encoding/decoding scheme is desired, the embedded General Purpose Serial Interface (GPSI) allows direct access to/from the MAC. In addition, the device provides programmable on-chip LED drivers for transmit, receive, collision, receive polarity, link integrity and activity, or jabber status. The PCnet-ISA II controller also provides an External Address Detection Interface TM (EADI TM ) to allow external hardware address filtering in internetworking applications.