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                                                15 December 2003.  SMS.

      Macintosh 25-Pin SCSI Cable

   This document describes a SCSI cable intended to connect a
Macintosh-compatible DB25 SCSI port to an Amp 50-pin SCSI port.

   On the DB25 connector, pins 7, 9, 14, 16, 18. and 24 are grounds.  On
the Amp 50-pin connector, pins 1-12 and 14-25 are grounds, and pin 13 is
not connected.  Exactly which ground pins on each connector are
connected together is normally not critical.  The table below shows the
arrangement of grounds in one commercial cable, but other arrangements
could work equally well.


      SCSI     DB25   Amp-50

     -REQ        1      49
     -MSG        2      46
     -I/O        3      50
     -RST        4      45
     -ACK        5      44
     -BSY        6      43
     (gnd)       7      16, 18, 19
     -DB(0)      8      26
     (gnd)       9      20, 21, 22
     -DB(3)     10      29
     -DB(5)     11      31
     -DB(6)     12      32
     -DB(7)     13      33
     (gnd)      14      1, 2, 3
     -C/D       15      48
     (gnd)      16      4, 5, 6
     -ATN       17      41
     (gnd)      18      7, 8, 9, 11
     -SEL       19      47
     -DB(P)     20      34
     -DB(1)     21      27
     -DB(2)     22      28
     -DB(4)     23      30
     (gnd)      24      23, 24, 25
     TERMPWR    25      38


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© 2008 Steven M. Schweda.