RL11 disk controller

The RL11 disk controller for the UNIBUS was for the RL01 and RL02 disk drives.

The RL11 was a hex board, with a 40-pin Berg connector holding a cable to the first drive. Up to 4 drives can be connected to a single controller, using a bus running from one drive to the next, with a terminator in the last drive of the string.

The controller and drive combination can execute 8 different commands:

• No Operation
• Write Check
• Get Status
• Seek
• Read Header
• Write Data
• Read Data
• Read Data Without Header Check

Spiral reads and writes (i.e. multi-block reads which start on one track, and overflow to the next) are not supported; multiple separate read/write commands are needed, with a seek to the next track between each pair.

Device registers

The RL11 controller includes 4 read-write registers:

Register	Abbreviation	Address
Control Status Register	RLCS	774400
Bus Address Register	RLBA	774402
Disk Address Register	RLDA	774404
Multipurpose Register	RLMP	774406

774400: Control Status Register (RLCS)

CERR	DE	NXM	DLT/HNF	DCRC/ HCRC	OPI	DRVSEL		CRDY	IE	ADDR EX		FUNC			DRDY
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

774402: Bus Address Register (RLBA)

BA15 <---> BA01															0
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

774404: Disk Address Register (RLDA)

During a 'Seek' command:

0	CYL ADDR DIFF								RSVD		HD SEL	0	DIR	0	1
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

During a 'Read Data' or 'Write Data' command:

0	CYL ADDR								HD SEL	SECTOR
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

During a 'Get Status' command:

NOT USED								MBZ				RESET	0	GT STA	1
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

774406: Multipurpose Register (RLMP)

During a 'Get Status' command:

WDE	CHE	WL	SKTO	SPE	WGE	VC	DSE	Rsvd	HS	CO	HO	BH	STATE
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

State Code	State
0	Load Cartridge
1	Spin Up
2	Brush Cycle
3	Load Heads
4	Seek
5	Lock On
6	Unload Heads
7	Spin Down

During a 'Read Header' command, three successive reads to the Multipurpose Register will return:

0	CYL ADDR								HD SEL	SECTOR
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

in the first word, all 0's in the second word, and the header CRC in the third.

During a 'Read Data' or 'Write Data' command:

111			WC
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00