Mico Dual Serial Interface for Pdp8/e/f/m

This document provides a technical overview and firmware analysis of the MICO Dual Serial Interface module designed for PDP-8 OMNIBUS computer systems (such as the PDP-8/e, f, m, and a). Because no official manufacturer documentation was available, the author reverse-engineered the module by analyzing the PCB layout and disassembling the onboard firmware.

Key features of the document include:

• System Overview: The module consists of an OMNIBUS interface and an I/O area containing a Z80 microprocessor core (running at 4 MHz with 1 KB ROM and 1 KB RAM), two Z80 PIOs, two 8251 PUSARTs for serial communication, a Z80 CTC (counter/timer), and a dual baud rate generator.
• Configuration: Detailed tables are provided for device code selection via onboard octal switches, baud rate selection, and serial communication mode settings (stop bits, parity, data bits).
• Technical Maps: Includes complete memory and I/O address maps required for interfacing the module with the host PDP-8 system.
• Firmware Analysis: The document concludes with a fully commented assembly listing of the module's firmware, detailing the initialization sequences, interrupt service routines, and the main loop used for servicing the serial and parallel interfaces.

Disclaimer: The author explicitly states that no warranties are provided regarding the correctness or usability of the information contained in the document.