Appendix A.     SCSI Connectors


A.1.    25 pin DB-25 SCSI connector

        The DB-25 connector is the one looking like a PC's printer port.
        I think Apple introduced this DB-25 connector for SCSI, but I'm
        not sure about it. The Macintosh Plus didn't supply Termination
        power, so pin 25 isn't connected with this model.
        Future Domain had a different DB-25 connector on their first
        adapters and adopted the Apple pinout scheme on their TMCxxxM
        SCSI host adapters later. Also, the M-models have a label
        "Apple pinout" somewhere on the slot plate.
        The adapters in question are the TMC-820, -830, -840, -845,
        -850, -860, -870, -875, -885 and MCS-350. If you need a cable
        for one of these, contact Future Domain for the cable with part
        number HCA-108.
        Extreme care should be taken if you get a Future Domain Cable
        or an adapter where you're not _absolutely_ sure if it's an old
        FD or an Apple-style device. Wrong connections will blow your TP
        fuse on the host adapter and - probably - destroy the host
        adapter or other devices on the SCSI bus !

        The pin counting is like:     1  2  3  4 ... 13
                                       14 15 16 ... 25

        Pin       Signal         Signal
                  Apple          old FD

         1        -REQ           GND
         2        -MSG           -DB(1)
         3        -I/O           -DB(3)
         4        -RST           -DB(5)
         5        -ACK           -DB(7)
         6        -BSY           GND
         7        Ground         -SEL
         8        -DB0           GND
         9        Ground         SPARE
        10        -DB3           -RST
        11        -DB5           -C/D
        12        -DB6           -I/O
        13        -DB7           GND
        14        Res./Ground    -DB(0)
        15        -C/D           -DB(2)
        16        Res./Ground    -DB(4)
        17        -ATN           -DB(6)
        18        Ground         -DB(P)
        19        -SEL           GND
        20        -DBP           -ATN
        21        -DB1           -MSG
        22        -DB2           -ACK
        23        -DB4           -BSY
        24        Ground         -REQ
        25      * Term. Power    GND        *: not connected in the
                                               Mac Plus connector.

A.2.    50 pin SCSI connectors

        Type  1 is the flat cable connector on the devices' PCB.
        Type  2 is the 50-pin Centronics-style connector, still the
                "Standard" PC SCSI connector
        The SCSI-2 high density connector's pinout is identical to the
        Type 2 Centronics-style connector

        Type 1    1 3 5 7 ..... 49     Type 2    1  2  3 ..... 25
        counts   Ŀ    counts   +/--------------\+
                               \______________/
                  2 4 6 8 ..... 50               26 27 28 .... 50


         Pin       Type                 Pin       Type
                Single-Ended                   Differential
                1          2                   1          2
                                   
          1     GND       GND            1     GND       GND
          2     -DB(0)    GND            2     GND       +DB(0)
          3     GND       GND            3     +DB(0)    +DB(1)
          4     -DB(1)    GND            4     -DB(0)    +DB(2)
          5     GND       GND            5     +DB(1)    +DB(3)
          6     -DB(2)    GND            6     -DB(1)    +DB(4)
          7     GND       GND            7     +DB(2)    +DB(5)
          8     -DB(3)    GND            8     -DB(2)    +DB(6)
          9     GND       GND            9     +DB(3)    +DB(7)
         10     -DB(4)    GND           10     -DB(3)    +DB(P)
         11     GND       GND           11     +DB(4)    DIFFSENS
         12     -DB(5)    Res.          12     -DB(4)    Res.
         13     GND       n.c.          13     +DB(5)    TRMPWR
         14     -DB(6)    Res.          14     -DB(5)    Res.
         15     GND       GND           15     +DB(6)    +ATN
         16     -DB(7)    GND           16     -DB(6)    GND
         17     GND       GND           17     +DB(7)    +BSY
         18     -DB(P)    GND           18     -DB(7)    +ACK
         19     GND       GND           19     +DB(P)    +RST
         20     GND       GND           20     -DB(P)    +MSG
         21     GND       GND           21     DIFFSENS  +SEL
         22     GND       GND           22     GND       +C/D
         23     Res.      GND           23     Res.      +REQ
         24     Res.      GND           24     Res.      +I/O
         25     n.c.      GND           25     TRMPWR    GND
         26     TRMPWR    -DB0          26     TRMPWR    GND
         27     Res.      -DB1          27     Res.      -DB(0)
         28     Res.      -DB2          28     Res.      -DB(1)
         29     GND       -DB3          29     +ATN      -DB(2)
         30     GND       -DB4          30     -ATN      -DB(3)
         31     GND       -DB5          31     GND       -DB(4)
         32     -ATN      -DB6          32     GND       -DB(5)
         33     GND       -DB7          33     +BSY      -DB(6)
         34     GND       -DBP          34     -BSY      -DB(7)
         35     GND       GND           35     +ACK      -DB(P)
         36     -BSY      GND           36     -ACK      GND
         37     GND       Res.          37     +RST      Res.
         38     -ACK      TRMPWR        38     -RST      TRMPWR
         39     GND       Res.          39     +MSG      Res.

         Pin       Type                 Pin       Type
                Single-Ended                   Differential
                1          2                   1          2
                                   
         40     -RST      GND           40     -MSG      -ATN
         41     GND       -ATN          41     +SEL      GND
         42     -MSG      GND           42     -SEL      -BSY
         43     GND       -BSY          43     +C/D      -ACK
         44     -SEL      -ACK          44     -C/D      -RST
         45     GND       -RST          45     +REQ      -MSG
         46     -C/D      -MSG          46     -REQ      -SEL
         47     GND       -SEL          47     +I/O      -C/D
         48     -REQ      -C/D          48     -I/O      -REQ
         49     GND       -REQ          49     GND       -I/O
         50     -I/O      -I/O          50     GND       GND

        There is a DB-50 connector (three-row) variant in SCSI-1 that
        Sun Microsystems used for older peripherals, but it's normally
        not used any more. However, if you need the layout, holler, and
        I'll search for it.


A.3.    68 pin SCSI connectors

         Pin    Cable Type              Pin    Cable Type
                Single-Ended                   Differential
                 B         P                    B         P
                                   
          1     GND       GND            1     GND       +DB(12)
          2     GND       GND            2     +DB(8)    +DB(13)
          3     GND       GND            3     +DB(9)    +DB(14)
          4     GND       GND            4     +DB(10)   +DB(15)
          5     GND       GND            5     +DB(11)   +DB(P1)
          6     GND       GND            6     +DB(12)   GND
          7     GND       GND            7     +DB(13)   +DB(0)
          8     GND       GND            8     +DB(14)   +DB(1)
          9     GND       GND            9     +DB(15)   +DB(2)
         10     GND       GND           10     +DB(P1)   +DB(3)
         11     GND       GND           11     +ACKB     +DB(4)
         12     GND       GND           12     GND       +DB(5)
         13     GND       Open          13     +REQB     +DB(6)
         14     GND       GND           14     +DB(16)   +DB(7)
         15     GND       GND           15     +DB(17)   +DB(P)
         16     GND       GND           16     +DB(18)   DIFFSENS
         17     TRMPWRB   TRMPWR        17     TRMPWRB   TRMPWR
         18     TRMPWRB   TRMPWR        18     TRMPWRB   TRMPWR
         19     GND       Res./GND      19     +DB(19)   Res.
         20     GND       GND           20     +DB(20)   +ATN
         21     GND       GND           21     +DB(21)S  GND
         22     GND       GND           22     +DB(22)   +BSY
         23     GND       GND           23     +DB(23)   +ACK
         24     GND       GND           24     +DB(P2)   +RST
         25     GND       GND           25     +DB(24)   +MSG
         26     GND       GND           26     +DB(25)   +SEL
         27     GND       GND           27     +DB(26)   +C/D
         28     GND       GND           28     +DB(27)   +REQ
         29     GND       GND           29     +DB(28)   +I/O
         30     GND       GND           30     +DB(29)   GND
         31     GND       GND           31     +DB(30)   +DB(8)
         32     GND       GND           32     +DB(31)   +DB(9)
         33     GND       GND           33     +DB(P3)   +DB(10)
         34     GND       GND           34     GND       +DB(11)
         35     GND       -DB(12)       35     GND       -DB(12)
         36     -DB(8)    -DB(13)       36     -DB(8)    -DB(13)
         37     -DB(9)    -DB(14)       37     -DB(9)    -DB(14)
         38     -DB(10)   -DB(15)       38     -DB(10)   -DB(15)
         39     -DB(11)   -DB(P1)       39     -DB(11)   -DB(P1)
         40     -DB(12)   -DB(0)        40     -DB(12)   GND
         41     -DB(13)   -DB(1)        41     -DB(13)   -DB(0)
         42     -DB(14)   -DB(2)        42     -DB(14)   -DB(1)
         43     -DB(15)   -DB(3)        43     -DB(15)   -DB(2)
         44     -DB(P1)   -DB(4)        44     -DB(P1)   -DB(3)
         45     -ACKB     -DB(5)        45     -ACKB     -DB(4)
         46     GND       -DB(6)        46     DIFFSENS  -DB(5)
         47     -REQB     -DB(7)        47     -REQB     -DB(6)
         48     -DB(16)   -DB(P)        48     -DB(16)   -DB(7)
         49     -DB(17)   GND           49     -DB(17)   -DB(P)
         50     -DB(18)   GND           50     -DB(18)   GND
         51     TRMPWRB   TRMPWR        51     TRMPWRB   TRMPWR
         52     TRMPWRB   TRMPWR        52     TRMPWRB   TRMPWR

         Pin    Cable Type              Pin    Cable Type
                Single-Ended                   Differential
                B          P                   B          P
                                   
         53     -DB(19)   Res.          53     -DB(19)   Res.
         54     -DB(20)   GND           54     -DB(20)   -ATN
         55     -DB(21)   -ATN          55     -DB(21)   GND
         56     -DB(22)   GND           56     -DB(22)   -BSY
         57     -DB(23)   -BSY          57     -DB(23)   -ACK
         58     -DB(P2)   -ACK          58     -DB(P2)   -RST
         59     -DB(24)   -RST          59     -DB(24)   -MSG
         60     -DB(25)   -MSG          60     -DB(25)   -SEL
         61     -DB(26)   -SEL          61     -DB(26)   -C/D
         62     -DB(27)   -C/D          62     -DB(27)   -REQ
         63     -DB(28)   -REQ          63     -DB(28)   -I/O
         64     -DB(29)   -I/O          64     -DB(29)   GND
         65     -DB(30)   -DB(8)        65     -DB(30)   -DB(8)
         66     -DB(31)   -DB(9)        66     -DB(31)   -DB(9)
         67     -DB(P3)   -DB(10)       67     -DB(P3)   -DB(10)
         68     GND       -DB(11)       68     GND       -DB(11)

A.4.    110 pin SCSI connector ("L"-cable)

        Pin     Single    Diff.        Pin     Single    Diff.
                Ended                          Ended
                                   
          1     GND       GND           56     GND       GND
          2     GND       +DB(24)       57     -DB(24)   -DB(24)
          3     GND       +DB(25)       58     -DB(25)   -DB(25)
          4     GND       +DB(P6)       59     -DB(P6)   -DB(P6)
          5     GND       +DB(27)       60     -DB(27)   -DB(27)
          6     GND       +DB(28)       61     -DB(28)   -DB(28)
          7     GND       +DB(29)       62     -DB(29)   -DB(29)
          8     GND       +DB(30)       63     -DB(30)   -DB(30)
          9     GND       +DB(31)       64     -DB(31)   -DB(31)
         10     GND       +DB(P3)       65     -DB(P3)   -DB(P3)
         11     GND       +DB(12)       66     -DB(12)   -DB(12)
         12     GND       +DB(13)       67     -DB(13)   -DB(13)
         13     GND       +DB(14)       68     -DB(14)   -DB(14)
         14     GND       +DB(15)       69     -DB(15)   -DB(15)
         15     GND       +DB(P1)       70     -DB(P1)   -DB(P1)
         16     GND       GND           71     -DB(0)    GND
         17     GND       -DB(0)        72     -DB(1)    -DB(0)
         18     GND       -DB(1)        73     -DB(2)    -DB(1)
         19     GND       -DB(2)        74     -DB(3)    -DB(2)
         20     GND       -DB(3)        75     -DB(4)    -DB(3)
         21     GND       -DB(4)        76     -DB(5)    -DB(4)
         22     GND       -DB(5)        77     -DB(6)    -DB(5)
         23     GND       -DB(6)        78     -DB(7)    -DB(6)
         24     GND       -DB(7)        79     -DB(P)    -DB(7)
         25     GND       -DB(P)        80     GND       -DB(P)
         26     GND       DIFFSENS      81     GND       GND
         27     TRMPWR    TRMPWR        82     TRMPWR    TRMPWR
         28     TRMPWR    TRMPWR        83     TRMPWR    TRMPWR
         29     TRMPWR    TRMPWR        84     TRMPWR    TRMPWR
         30     GND       +ATN          85     GND       -ATN
         31     GND       GND           86     -ATN      GND
         32     GND       +BSY          87     GND       -BSY
         33     GND       +ACK          88     -BSY      -ACK
         34     GND       +RST          89     -ACK      -RST
         35     GND       +MSG          90     -RST      -MSG
         36     GND       +SEL          91     -MSG      -SEL
         37     GND       +C/D          92     -SEL      -C/D
         38     GND       +REQ          93     -C/D      -REQ
         39     GND       +I/O          94     -REQ      -I/O
         40     GND       GND           95     -I/O      GND
         41     GND       +DB(8)        96     -DB(8)    -DB(8)
         42     GND       +DB(9)        97     -DB(9)    -DB(9)
         43     GND       +DB(10)       98     -DB(10)   -DB(10)
         44     GND       +DB(11)       99     -DB(11)   -DB(11)
         45     GND       GND          100     GND       GND
         46     GND       +DB(16)      101     -DB(16)   -DB(16)
         47     GND       +DB(17)      102     -DB(17)   -DB(17)
         48     GND       +DB(18)      103     -DB(18)   -DB(18)
         49     GND       +DB(19)      104     -DB(19)   -DB(19)
         50     GND       +DB(20)      105     -DB(20)   -DB(20)
         51     GND       +DB(21)      106     -DB(21)   -DB(21)
         52     GND       +DB(22)      107     -DB(22)   -DB(22)
         53     GND       +DB(23)      108     -DB(23)   -DB(23)
         54     GND       +DB(P2)      109     -DB(P2)   -DB(P2)
         55     GND       GND          110     GND       GND

A.5.    IBM 60 pin SCSI Connector

        For whatever reason, IBM defined an own 60 pin SCSI connector
        for their PS/2 and RS/6000 systems. It is a high density
        SCSI-2/3 style mini-centronics connector and the first 50 pins
        are identical to 'standard' SCSI-2 HD connectors. If you have
        a newer RS/6000 with the embedded SCSI-2 host adapter, it
        should have the SCSI-2 standard connector.
        I couldn't find an application where the remaining 10 pins
        are used, but who knows.... Somewhere i read that this
        connector should have been the official SCSI-2 connector,
        but was later withdrawed for the 50-pin types.

        Pin     Signal         Pin     Signal
                           
          1     GND             31     GND
          2     -DB(0)          32     -ATN
          3     GND             33     GND
          4     -DB(1)          34     GND
          5     GND             35     GND
          6     -DB(2)          36     -BSY
          7     GND             37     GND
          8     -DB(3)          38     -ACK
          9     GND             39     GND
         10     -DB(4)          40     -RST
         11     GND             41     GND
         12     -DB(5)          42     -MSG
         13     GND             43     GND
         14     -DB(6)          44     -SEL
         15     GND             45     GND
         16     -DB(7)          46     -C/D
         17     GND             47     GND
         18     -DB(P)          48     -REQ
         19     GND             49     GND
         20     GND             50     -I/O
         21     GND             51     GND       -- from pin 51 on
         22     GND             52     Reserved     IBM's extensions
         23     Res./GND        53     Reserved
         24     Res./GND        54     Reserved
         25     n.c.            55     Reserved
         26     TRMPWR          56     Reserved
         27     Reserved        57     Reserved
         28     Reserved        58     Reserved
         29     GND             59     Reserved
         30     GND             60     Reserved


A.6.    Other SCSI connectors

        Sometimes, for many reasons, some of them strange to me <g>,
        a company decides to introduce a new SCSI connector.

A.6.1.  Apple PowerBook HDI-30 connector

        One of those is the Apple PowerBook's HDI-30 connector.
        Its signals make me think they tried a small hop into the SCA
        direction, as it also supplies power to the drive ...

        Apple's external HDI-30 SCSI connector has the following pinout:

          Pin     Internal      External
                  Connector     Connector

           1      DISK.+5       -LINK.SEL       -- I have no idea what
           2      DISK.+5       -DB(0)          -- -LINK.SEL is for.
           3      Ground        Ground
           4      Ground        -DB(1)
           5      Ground        TERMPWR         Pin 5 (TP) is not used
           6      -DB(0)        -DB(2)          by Apple ("reserved for
           7      -DB(1)        -DB(3)          future use") and is not
           8      -DB(2)        Ground          connected in Apple's
           9      -DB(3)        -ACK            original PB SCSI cable.
          10      -DB(4)        Ground
          11      -DB(5)        -DB(4)
          12      -DB(6)        Ground
          13      -DB(7)        Ground
          14      -DB(P)        -DB(5)
          15      DISK.+5       Ground
          16      -BSY          -DB(6)
          17      -ATN          Ground
          18      -ACK          -DB(7)
          19      Ground        -DB(P)
          20      -MSG          Ground
          21      -RST          -REQ
          22      -SEL          Ground
          23      -C/D          -BSY
          24      -I/O          Ground
          25      -REQ          -ATN
          26      Ground        -C/D
          27      Ground        -RST
          28      Ground        -MSG
          29      DISK.+5       -SEL
          30      DISK.+5       -I/O


        When Novell designed their Disk Coprocessor Board (DCB), they
        took an own, proprietary SCSI connector (guess a reason <g>).
        Procomp took the same connector on their F-DCB and M-DCB host
        adapters to maintain 100% compatibility besides the register
        compatibility of the DCB board itself.
        This connection uses a DB-37 Sub-D connector, that at least
        has enough conductors to provide a dedicated ground wire for
        each signal.

        Novell's DCB with the original cable doesn't provide TERMPWR
        to the SCSI bus, although it is used locally for the terminator
        packs, so each terminated device must supply its own, local
        terminator power. Procomp does provide TERMPWR, but only with
        their own cable - they simple added this single wire.


        Novell/Procomp DCB external pinout
        Pin     Signal  Pin     Signal
			
        1       GND     20      -DB(0)
        2       GND     21      -DB(1)
        3       GND     22      -DB(2)
        4       GND     23      -DB(3)
        5       GND     24      -DB(4)
        6       GND     25      -DB(5)
        7       GND     26      -DB(6)
        8       GND     27      -DB(7)
        9       GND     28      -DB(P)
        10      GND     29      -ATN
        11      GND     30      -BSY
        12      GND     31      -ACK
        13      GND     32      -RST
        14      GND     33      -MSG
        15      GND     34      -SEL
        16      GND     35      -C/D
        17      GND     36      -REQ
        18      GND     37      -I/O
        19      TERMPWR *               * not connected on Novell DCB

        A special quirk in the Procomp DCB is, that it doesn't provide
        termination for the -ATN, -ACK and -RST signals. Without access
        to an original Novell DCB, i don't know if it has the same
        incomplete termination.


A.6.3.  Rumours about strange connectors...

        Over time i got a few questions on the Toshiba 150-pin SCSI
        connector - thanks to Don Whittemore now i can clearly state
        that this animal doesn't exist - it's only an ISA expansion
        connector, and Toshiba sold a SCSI host adapter for it with
        a matching connector called "PC-PA2113 150 pin SCSI adapter".


------- If you know of another special SCSI connector, please let
        me know. I'll try to include it here.


A.7.    Mixing SCSI-2 and Wide-SCSI devices - adapter wiring

        In the last time, more and more higher-end PCs are equipped
        with Wide-SCSI adapters and disk drives. As you would expect,
        this creates a new problem - how to connect 8-bit SCSI devices
        like CDROM or tape drives. Most adapters have an additional
        internal 8-bit connector, but what to do with external devices?
        The SCSI-3 drafts address this with a definition how 8-bit and
        16-bit devices must be wired together (SCSI-3 because the 'P'
        cable is a SCSI-3 part). Thanks to Michael Arellano, who
        provided a proven wiring diagram for the drafted circuit.

        According to the drafts, 8-bit devices shall leave the upper
        byte signal lines DB(8) to DB(15) and DB(P1) open, and connect
        the "standard" lines as usual. Together with the clever layout
        of the connectors, this makes it possible to include one or
        more 8-bit connectors in a Wide-SCSI cable.
        However, with all the high density connectors it isn't easy to
        make such a cable yourself, so, if you think about it, be sure
        that you have the neccessary equipment and tools before you
        invest in the connectors - they're expensive.

        16 Bit Wide-SCSI to 8 Bit SCSI wiring diagram, Single Ended:

        68-pin     Signal    50-pin     68-pin    Signal      50-pin
                                    
         1          GND                 35         -DB(12)
         2          GND                 36         -DB(13)
         3          GND                 37         -DB(14)
         4          GND                 38         -DB(15)
         5          GND                 39         -DB(P1)
         6          GND        1        40         -DB(0)      26
         7          GND        2        41         -DB(1)      27
         8          GND        3        42         -DB(2)      28
         9          GND        4        43         -DB(3)      29
        10          GND        5        44         -DB(4)      30
        11          GND        6        45         -DB(5)      31
        12          GND        7        46         -DB(6)      32
        13          Open       8        47         -DB(7)      33
        14          GND        9        48         -DB(P)      34
        15          GND       10        49         GND         35
        16          GND       11        50         GND         36
        17          TRMPWR    12        51         TRMPWR      37
        18          TRMPWR    13        52         TRMPWR      38
        19          Res./GND  14        53         Res.        39
        20          GND       15        54         GND         40
        21          GND       16        55         -ATN        41
        22          GND       17        56         GND         42
        23          GND       18        57         -BSY        43
        24          GND       19        58         -ACK        44
        25          GND       20        59         -RST        45
        26          GND       21        60         -MSG        46
        27          GND       22        61         -SEL        47
        28          GND       23        62         -C/D        48
        29          GND       24        63         -REQ        49
        30          GND       25        64         -I/O        50
        31          GND                 65         -DB(8)
        32          GND                 66         -DB(9)
        33          GND                 67         -DB(10)
        34          GND                 68         -DB(11)


A.8.    SCA Single Ended connector

        The Single Connector Attachment uses an 80-pin connector
        to supply all neccessary SCSI signals, control signals, LED
        and power connections.

        The SCA connector uses two different pin lengths to ensure
        defined signal states on hot-plugging. I'll explain this
        mechanism in slightly more detail in the SCA definition in
        chapter 1.


         Pin    Signal              Pin     Signal

          1     12 VOLT CHARGE      41      12 V GROUND
          2     12 VOLT             42      12 V GROUND
          3     12 VOLT             43      12 V GROUND
          4     12 VOLT             44      MATED 1
          5     RESERVED/NC         45      RESERVED/NC
          6     RESERVED/NC         46      DIFFSNS
          7     - DB(11)            47      GROUND
          8     - DB(10)            48      GROUND
          9     - DB(9)             49      GROUND
         10     - DB(8)             50      GROUND
         11     - I/O               51      GROUND
         12     - REQ               52      GROUND
         13     - C/D               53      GROUND
         14     - SEL               54      GROUND
         15     - MSG               55      GROUND
         16     - RST               56      GROUND
         17     - ACK               57      GROUND
         18     - BSY               58      GROUND
         19     - ATN               59      GROUND
         20     - DB(P0)            60      GROUND
         21     - DB(7)             61      GROUND
         22     - DB(6)             62      GROUND
         23     - DB(5)             63      GROUND
         24     - DB(4)             64      GROUND
         25     - DB(3)             65      GROUND
         26     - DB(2)             66      GROUND
         27     - DB(1)             67      GROUND
         28     - DB(0)             68      GROUND
         29     - DB(P1)            69      GROUND
         30     - DB(15)            70      GROUND
         31     - DB(14)            71      GROUND
         32     - DB(13)            72      GROUND
         33     - DB(12)            73      GROUND
         34     5 VOLT              74      MATED 2
         35     5 VOLT              75      5 V GROUND
         36     5 VOLT CHARGE       76      5 V GROUND
         37     SYNC                77      ACTIVE LED OUT
         38     RMT_START           78      DLYD_START
         39     SCSI ID(0)          79      SCSI ID (1)
         40     SCSI ID (2)         80      SCSI ID (3)

