DMC11 IPL Microprocessor User's Manual

This user manual describes the DMC11 IPL Microprocessor, a product by Digital Equipment Corporation (DEC) from September 1976, designed for PDP-11 computer systems.

The DMC11 is a network link composed of a microprocessor module (M8200-YA/YB) and a line unit module (M8201/M8202). Its primary function is to provide a full-duplex parallel data interface between a PDP-11 central processor and a communication line.

Key aspects of the DMC11 include:

• Protocol Implementation: It implements the DDCMP (Digital Data Communications Message Protocol) in firmware (via ROM-based microcode), handling error detection (using a 16-bit Cyclic Redundancy Check, CRC-16) and correction (automatic retransmissions).
• Benefits: By offloading protocol processing, the DMC11 simplifies programming, conserves PDP-11 memory and processor time, and enhances data throughput (operating at speeds up to 1 Mbps locally and 56 Kbps remotely).

• Connectivity Options:

  • M8201 (low-speed line unit): Interfaces with external synchronous modems (EIA/CCITT V24 or V35 compatible) for remote communication.
  • M8202 (high-speed line unit): Includes an integral modem for local network connections via coaxial cables.

• Features: It supports down-line loading of satellite computer systems, remote initialization (Remote Load Detect), power fail recovery without data loss, and 16-bit NPR (DMA) transfers.

• System Interface: The PDP-11 interacts with the DMC11 through its Control and Status Registers (CSRs) via the Unibus. The DMC11 manages data transfers by queuing buffers and notifying the PDP-11 of completion or error conditions.
• Installation: The manual provides instructions for physically installing the modules, selecting "floating" device and vector addresses via DIP switches, and running diagnostic tests.