TM11 magtape controller

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The TM11, TMA11 and TMB11 magnetic tape controllers are a series of UNIBUS device controllers, used with a number of different 1/2" magnetic tape drives from DEC. They are all compatible, both in their interface to the drives, and in their programming interface.

The TM11 and TMA11 are almost identical in construction; they are implemented as a series of smaller standard FLIP CHIPs in a custom-wired 19" backplane.

M7911 card from a TMB11

The TMB11 is a re-implementation, using two larger custom boards - one hex (M7912) and one quad (M7911) - along with 4 generic (i.e. not device-unique) UNIBUS-specific FLIP CHIPs (M105, M795, M796, M7821); all of which plug into a custom hex-high four-slot system unit backplane (for a BA11, etc box), DEC part number 70-12678.


The TM11 series controllers connect to a 'Master drive', which includes considerable extra electronics; additional 'Slave' drives may be connected to the Master drive.

Much of the extra functionality is related to the operation of the drive (CRC, etc); however, the TM11 series controllers generate a Positive bus, which a Master drive (depending on the drive type in use) converts to a Negative bus for the Slave drives - Slave drives of some types have a Negative bus only.

The TM11 series controllers were initially used with the TU10 magtape drives, for which the slaves are all Negative bus. Later, they were used with the TS03 drive (for which the Master drive includes an M8920 board, to interface to a TM11). They were also used with the TU10W drive (which is the later TU16 drive, without the TM02 controller); and the TE16 drive, when it is upgraded to TE10W (Positive bus - Master and Slave) or TE10N (Negative bus - Slave).

Device registers

Register Abbreviation Address
Status Register MTS 772520
Command Register MTC 772522
Byte Record Counter MTBRC 772524
Current Memory Address Register MTCMA 772526
Data Buffer MTD 772530
TU10 Read Lines MTRD 772532

772520: Status Register (MTS)

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

772522: Command Register (MTC)

ERR DEN8-5 PCLR PEVN Unit Select CUR INT ENB Extended Memory Function GO
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

772524: Byte Record Counter (MTBRC)

BC15 <---> BC00
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

772526: Current Memory Address Register (MTCMA)

MA15 <---> MA00
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

772530: Data Buffer (MTD)

Data (read-only) Data (read/write)
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

772532: TU10 Read Lines (MTRD)

Timer CRC/LPCC selector BTE error Gap shutdown Unused Parity Data
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

Drive bus

The connection to the master drive is a standard dual-width BC11-A cable, as used for the UNIBUS. This is the pinout for the TM11 (the other two are basically identical to this):

Pin Signal
Use Source Pin Signal
Use Source
AA1 SEL0 Tape unit select Controller AA2
AB1 SEL1 AB2 Ground
AD1 AD2 WD0 Write Data Controller
AE1 DEN0 Density
(see table below)
Controller AE2 WD1
AJ1 WXG Write Extended Gap Controller AJ2 WD4
AK1 FWD Tape Forward AK2 WD5
AL1 RWD Tape Rewind AL2 WD6
AM1 WRE Write Enable AM2 WD7
AN1 Ground AN2 REV Tape reverse Controller
AP1 AP2 CINIT Initialize
AR1 AR2 SET Required to start any tape operation
AS1 AS2 WDR Write Data Ready
AT1 AT2 PEVN Even Parity
AU1 AU2 WFMK Write File Mark
AV1 AV2 Ground
BA1 RDS Read Strobe Drive BA2
BB1 SDWN Tape Settle Down BB2 Ground
BC1 TUR Tape Unit Ready BC2
BD1 Ground BD2 WRS Write Strobe Drive
BF1 RD0 Read Data Drive BF2 RWS Rewind Status
BK1 RD3 BK2 BOT Beginning of Tape Drive
BL1 RD4 BL2 WRL Write Lock
BM1 RD5 BM2 VPE Vertical Parity Error
BN1 RD6 BN2 SELR Select Remote
BP1 RD7 BP2 7CH 7-Track Unit
BR1 RDP Read Parity Bit Drive BR2 EOT End of Tape
BS1 FMK File Mark Read BS2 CRCE CRC Error
BT1 Ground BT2 LRCE Longitudinal Parity Error
BU1 BU2 LRCS Longitudinal Parity Strobe
BV1 MAN CLR L BV2 Ground

For the TMA11 and TMB11, delete the "MAN CLR L", and re-name "DEN0" and "DEN1" to "DEN8" and "DEN5" respectively. The encoding of the two density bits is:

DEN 5 DEN 8 Mode
0 0 200 bpi, 7-channel
0 1 800 bpi, 7-channel
1 0 556 bpi, 7-channel
1 1 800 bpi, 9-channel

Module Count Table

The following table gives a listing of the FLIP CHIPs used in the TM11. (Drawn from module count charts, confirmed in module utilization drawings.)

Single height boards:

Type Count Function
G736 1 Jumper Module
M105 1 UNIBUS Address Selector
M111 5$ Sixteen Inverters
M112 3 Ten 2-input NOR Gates
M113 7$ Ten 2-input NAND Gates
M115 2 Eight 3-input NAND Gates
M117 1 Six 4-input NAND Gates
M121 2 Six AND/NOR Gates
M127 3 Three 2-2-2-3 AND/NOR Gate
M149 4 Nine 2-input NAND Wired OR Matrix
M163 1 Dual Binary-to-Octal Decoder
M203 1 Eight S/R Flip-Flops
M205 2 Five D Flip-Flops
M216 5 Six D Flip-Flops
M239 1 Three 4-bit Counter Registers
M304 2 Four One-Shot Delays
M307 1 Two Integrating One-Shot
M627 3 Six NAND Power Amplifiers
M688 1 UNIBUS Power Fail Driver
M7821 1 UNIBUS Interrupt Control
M784 1 UNIBUS Receiver
M785 1 UNIBUS Transceiver
M796 1 UNIBUS Master Control
M797 1 Register Selection
M798 1 UNIBUS Drivers

$ = The module count table in the TM11 manual gives a different number, but that manual seems to be wrong; the prints, and an actual unit, have the number given here.

Double height boards:

  • M795 - Word Count and Current Memory Address

The table in the TM11 manual calls for two of these, but this is clearly wrong.

Module Locations

These are the module locations for the TM11:

Slot Connector A Connector B
5 M111 M627
6 M111 M901@
7 M798 G736
8 M149 M149
9 M105 M784
10 M7821 M785
11 M796 M797
12 M795
13 M149 M149
14 M216 M205
15 M163 M112
16 M113 M111
17 M115 M121
18 M216 M216
19 M121 M113
20 M117 M627
21 M239 M113
22 M115 M205
23 M111 M127
24 M216 M127
25 M112 M127
26 M112 M111
27 M113 M901@
28 M203 M688
29 M113 M113
30 M304 M627
31 M307 M216
32 M304 M113

@ = Cable

For the TMA11, slot 27B contains an M7854 "OPI/BTE Detector".

External links