View source for RK611 disk controller

The '''RK611 disk controller''' is the [[UNIBUS]] [[device controller]] for the [[RK06/07 disk drive|RK06 and RK07]] moving-[[head]] magnetic removable cartridge [[disk]] [[drive]]s. All data transfers are done using [[Direct Memory Access|DMA]]. Data is protected with a [[hardware]]-generated and checked [[error-correcting code]] (ECC); corrections (up to 11 bits) are done in [[software]].

==Implementation==

The RK611 consists of a specially wired 9-slot [[backplane]] and five [[DEC card form factor|hex]] cards; these are:

[[Image:RK611-M7904.jpg|250px|right|thumb|An M7904 card, showing the connector to the drive]]

{| border=1 !! Board number !! Function 
|-
| M7900 || UNIBUS interface module
|-
| M7901 || Register module
|-
| M7902 || Control module
|-
| M7903 || Data module
|-
| M7904 || Drive interface module
|}

At least three of the other slots are wired as UNIBUS [[Small Peripheral Controller|SPC]] slots (and thus require [[G727 grant continuity card]]s to be inserted when no device is plugged into them); the status of the fourth appears to be 'unused'. The quad slot on the end is necessarily a plain SPC slot; the other hex slots are apparently [[Modified UNIBUS Device|MUD]] slots.

One RK611 can control up to 8 drives; a [[flat cable]] plugs into a [[Berg connector]] on one of the cards, and runs to a transition adapter on the back of the rack. From there, a round cable runs to the first drive, and similar cables connect the rest of the drives, in series. A [[terminator]] must be plugged into the 'out' port of the last drive in the series.

===Backplane layout===

Board locations (as seen from the board insertion side of the backplane, not the [[wire-wrap]] pin side, as is common in [[DEC]] documentation) are:

{| class="wikitable"
! !! colspan="6" | Connector
|-
! Slot !! A !! B !! C !! D !! E !! F
|-
| 1 || colspan="2" style="text-align:center;" | UNIBUS In || colspan="4" style="text-align:center;" | SPC
|-
| 2 || colspan="6" style="text-align:center;" | MUD/SPC
|-
| 3 || colspan="6" style="text-align:center;" | MUD/SPC
|-
| 4 || colspan="6" style="text-align:center;" | M7904 Drive interface
|-
| 5 || colspan="6" style="text-align:center;" | M7903 Data
|-
| 6 || colspan="6" style="text-align:center;" | M7902 Control
|-
| 7 || colspan="6" style="text-align:center;" | M7901 Register
|-
| 8 || colspan="6" style="text-align:center;" | M7900 UNIBUS interface
|-
| 9 || colspan="2" style="text-align:center;" | UNIBUS Out || colspan="4" style="text-align:center;" | Unused?
|}

==Registers==

The RK611 has no less than fifteen [[register]]s:

{| border=1
! Register !! Abbreviation !! Address
|-
| Control and Status Register 1   || RKCS1  || 777440
|-
| Word Count Register             || RKWC   || 777442
|-
| Bus Address Register            || RKBA   || 777444
|-
| Disk Address Register           || RKDA   || 777446
|-
| Control and Status Register 2   || RKCS2  || 777450
|-
| Drive Status Register           || RKDS   || 777452
|-
| Error Register                  || RKES   || 777454
|-
| Attention Summary and Offset    || RKAS   || 777456
|-
| Desired Cylinder Register       || RKDC   || 777460
|-
| Data Buffer Register            || RKDB   || 777464
|-
| Maintenance Register 1          || RKMR1  || 777466
|-
| ECC Position Register           || RKECPS || 777470
|-
| ECC Pattern Register            || RKECPT || 777472
|-
| Maintenance Register 2          || RKMR2  || 777474
|-
| Maintenance Register 3          || RKMR3  || 777476
|}

The [[address]]es given assume the standard base address (0777440); if this is changed, so will the addresses. Note also that there is no register at 777462.
<!--
===7775440: Control and Status Register 1 (RKCS1)===

{{16bit-header}}
| Error || Block Check || Clear Leader || Write Lock || File Gap || Timing Error || Off Line || Unit Select || Transfer Request || Interrupt Enable || Ready || Last Byte || colspan=3 | Function || Go
{{16bit-bitout}}
-->
==External links==

* [http://www.bitsavers.org/pdf/dec/disc/rk06_rk07/EK-RK067-UG-001.pdf RK06/RK07 Disk Drive User's Manual] (EK-RK067-UG-001) - The RK611 is covered in Chapter 7
* [http://www.bitsavers.org/pdf/dec/unibus/MP00105_RK611_schem_Aug77.pdf RK611 Field Maintenance Print Set] (MP00105)

[[Category: UNIBUS Storage Controllers]]