DEPCA

This document is the PCSA DEPCA Hardware Reference Manual, published in April 1989 by Digital Equipment Corporation.

It serves as a technical reference for programmers wishing to program the Digital Ethernet Personal Computer Adapter (DEPCA) at the hardware level. The DEPCA is a full-length card designed for IBM Personal Computer, XT, AT, and compatibles, providing both an Ethernet network interface and a mouse interface.

Key aspects covered include:

• Introduction to the DEPCA: Describing its components, buffer RAM and ROM, and jumper configurations for I/O address ranges, memory allocation, interrupt vector selections, and remote boot.
• Network Interface Hardware: Detailed functional description of the network interface's integrated circuits (Coax Transceiver Interface, Serial Interface Adapter, and the Local Area Network Controller for Ethernet - LANCE), along with instructions on programming the LANCE, register descriptions, and explanations of data structures like initialization blocks, receive/transmit descriptor rings, and data buffers.
• Mouse Information: Outlining the mouse's communication requirements (asynchronous serial interface at 4800 baud), available commands, and the format of its position and self-test reports.

The manual explicitly states that direct hardware-level programming is not the recommended approach, advising instead the use of the data-link layer (firmware) as described in the Data Link Programmer's Reference Manual, as it offers no meaningful performance advantages and accounts for different LANCE chip revisions. It assumes the reader has a working knowledge of networking concepts and hardware programming.