DEC11-HRJPA-B-D RJP04 Disk Subsystem Maintenance Aug74

This document is a maintenance manual for the Digital Equipment Corporation (DEC) RJP04 moving head disk subsystem, providing detailed information for installation, operation, and servicing.

The RJP04 subsystem comprises an RH11 Device Controller and one to eight RP04 Disk Drives. The RH11 interfaces with a PDP-11 processor via the Unibus for control and data transfers (including NPR cycles) and communicates with the RP04 drives via the Massbus. The Massbus is divided into an asynchronous control bus (for commands and status) and a synchronous data bus (for high-speed data transmission).

Key functionalities include:

• Data Transfer: The RH11 manages DMA (Direct Memory Access) transfers for Read, Write, and Write-Check operations, using a 66-word Silo (FIFO buffer) to compensate for Unibus NPR latency.
• Disk Operations: It supports various commands for disk positioning (Seek, Recalibrate, Offset, Unload) and housekeeping.
• Data Format & Error Correction: RP04 drives support 16-bit or 18-bit data formats, featuring a detailed sector structure with headers (including cylinder, sector/track addresses, key words, and CRC) and data fields. The system incorporates an Error Correcting Code (ECC) (Burst Error Correcting Code) for detecting errors, with software-controlled correction.
• Comprehensive Error Handling: The manual extensively details various error conditions (e.g., Data Late, Write Check Error, Invalid Address, Unsafe conditions) and provides specific procedures for error classification, recovery, and clearing.
• Dual Controller Option: The subsystem supports configurations where two RH11 controllers can access the same set of RP04 drives, with mechanisms for managing drive access (unseized vs. seized states).

The manual also covers installation procedures (mechanical, electrical, and jumper configurations) and outlines the use of various diagnostic programs (MAINDEC series) for testing controller logic, drive mechanics, data paths, and error handling capabilities.