Dual Serial Interface

This document provides a technical overview and firmware disassembly for a dual serial interface module manufactured by MICO GmbH for PDP-8 OMNIBUS machines (e.g., PDP-8/e, /f, /m, and /a). Created due to a lack of existing manufacturer documentation, the guide covers the module's architecture, which includes the OMNIBUS interface and an I/O area containing a Z80 CPU, RAM, ROM, parallel interfaces (PIOs), and a serial interface (CTC and SIOs). It details the device code selection via switches, memory and I/O maps, serial baud rate configurations, and port pinouts. The latter half of the document provides a heavily commented firmware disassembly, outlining the initialization sequences, interrupt handling, and the main loop responsible for serial data management between the I/O area and the OMNIBUS.