RC11 disk controller

The RC11 device controller for the UNIBUS is a very early secondary storage controller for the PDP-11. It can handle up to 4 RS64 fixed-head disk drives, each with a capacity of 128 Kbytes of storage, organized in 32-word blocks.

The contents of each block are protected by a CRC.

Device registers

Register	Abbreviation	Address
Look Ahead Register	RCLA	777440
Disk Address Register	RCDA	777442
Disk Error Status Register	RCER	777444
Disk Control and Status Register	RCCS	777446
Word Count Register	RCWC	777450
Current Address Register	RCCA	777452
Maintenance Register	RCMN	777454
Data Buffer Register	RCDB	777456

777440: Look Ahead Register (RCLA)

Bad Address	Unused		Unit Number		Track Number					Sector Address
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777442: Disk Address Register (RCDA)

Unused			Unit Number		Track Number					Sector Address
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777444: Disk Error Status Register (RCES)

Data Late	Block Check	Data Sync	NXM	Unused		Timing Track	Unused	Address Parity	Sync Address	Disk Overflow	Missed Xfer	Unused
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777446: Disk Control and Status Register (RCCS)

Special Condition	Data Error	Address Error	Write Lock	NXD	Write Check	Inhibit Address	Abort	Ready	Interrupt Enable	Ext Mem		Mode	Function		Go
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777450: Word Count Register (RCWC)

WC15 <---> WC00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777452: Current Address Register (RCCA)

BA15 <---> BA01															Unused
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777454: Maintenance Register (RCMN)

Unit Select				Write Enable	Word Count	DMA Request	Address Found	Clock Polarity	DMA Enable	Data Track	Address Track	Phase Lock	Address Mark	Data Mark	Clock Track
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777456: Data Buffer Register (RCDB)

DB15 <---> DB00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

Implementation

The RC11 is composed of a number of boards (three quad, 5 single) mounted in a 4-slot system unit backplane. The quad cards are:

• M7219 - Bus Interface
• M7221 - Disk Interface
• M7222 - Status Control

Single:

• M7220 - Clock Control
• M7224 - Unit and Track Selector
• M7225 - Status Control Extender
• M796 - UNIBUS Master Control
• M782 Interrupt Control

External links

• RC11 disk control manual (DEC-11-HRCA-D)
• RC11 engineering drawings