UDA50 Maintenance Guide Nov82

This document is the UDA50 Maintenance Guide from Digital Equipment Corporation (DEC), published in 1982. It provides comprehensive procedures for the maintenance and troubleshooting of the UDA50 Disk Controller.

Key aspects covered include:

• Maintenance Philosophy: The guide emphasizes module replacement (specifically, the two hex modules M7161/M7162 or the upgraded M7485/M7486) rather than component-level repair by field service personnel.
• UDA50 Upgrades and Compatibility: It details differences in upgraded UDA50 modules (M7485/M7486), noting increased RAM size. A critical caution states that new and old UDA50 modules are not upward or downward compatible and must be replaced as a complete set.
• Configuration: Instructions are provided for setting UNIBUS address switches and jumpers, managing UNIBUS overloading (including a table of system-dependent delay configurations), and installing the priority plug.

• Diagnostic Features:

  • UDA50-Resident Diagnostics: PROM-based self-diagnostics that run on power-up, with success indicated by cycling LEDs. Specific LED error codes are provided to identify common faults.
  • UDA50 Host-Resident Diagnostics: Software diagnostics (for PDP-11 and VAX systems) designed to isolate subsystem faults to either the UNIBUS or the disk drives. These include disk formatter and exerciser programs.

• Fault Isolation and Troubleshooting: A troubleshooting flowchart is included, recommending starting with error logs. Detailed explanations are given for interpreting:

  • LED Error Codes
  • Status/Address (SA) Register Error Codes for more granular fault identification.
  • Real-Time Drive State (RTDS) messages, defining drive operational states (e.g., Off-line, Available, On-line) and the significance of various state bits.
  • Drive Status Bytes, providing a byte-by-byte breakdown of the detailed status reported by the drive.

• Related Documentation: The guide lists other Digital Equipment Corporation manuals for further reference, such as user guides, service manuals, and programmer's kits for the UDA50 and related disk drives.

• Bootstrap ROM Installation: Specifies the correct bootstrap ROMs to be installed for PDP-11 and VAX 11/750 systems.