SCSI Pin-Outs


  Internal SCSI Port (50-Pin Header)
  External SCSI Connector (High-density 50-pin) See External SCSI Connector.

  All odd pins are grounds, except for pin 25, which is unused.

   Pin 2: *Data 0
   Pin 4: *Data 1
   Pin 6: *Data 2
   Pin 8: *Data 3
  Pin 10: *Data 4
  Pin 12: *Data 5
  Pin 14: *Data 6
  Pin 16: *Data 7
  Pin 18: *Parity
  Pin 20: Ground
  Pin 22: Ground
  Pin 24: Ground
  Pin 26: Terminator Power
  Pin 28: Ground
  Pin 30: Ground
  Pin 32: *ATN
  Pin 34: Ground (Unused?)
  Pin 36: *BSY
  Pin 38: *ACK
  Pin 40: *RST
  Pin 42: *MSG
  Pin 44: *SEL
  Pin 46: *C/D
  Pin 48: *REQ
  Pin 50: *I/O
 

External SCSI Connector (DB25 Macintosh-Type Female Pseudo-SCSI)
(Note: This is by far the most common style of DB25 SCSI connector. Most [probably all] Amiga SCSI interfaces with DB25 connectors--like the A2091--use this pin-out.)

   Pin 1: *REQ
   Pin 2: *MSG
   Pin 3: *I/O
   Pin 4: *RST
   Pin 5: *ACK
   Pin 6: *BSY
   Pin 7: Ground
   Pin 8: *Data 0
   Pin 9: Ground
  Pin 10: *Data 3
  Pin 11: *Data 5
  Pin 12: *Data 6
  Pin 13: *Data 7
  Pin 14: Ground
  Pin 15: *C/D
  Pin 16: Ground
  Pin 17: *ATN
  Pin 18: Ground
  Pin 19: *SEL
  Pin 20: *Parity
  Pin 21: *Data 1
  Pin 22: *Data 2
  Pin 23: *Data 4
  Pin 24: Ground
  Pin 25: Terminator Power
 

External SCSI Connector (DB25 Future Domain-Type Female Pseudo-SCSI)
(Note: This is a rare alternate standard for the DB25 connector. It was only used on the Future Domain TMC-830/845 and TMC-850/860/885,  and is included here in case you end up with a cable meant for these boards.)

   Pin 1: Ground
   Pin 2: *Data 1
   Pin 3: *Data 3
   Pin 4: *Data 5
   Pin 5: *Data 7
   Pin 6: Ground
   Pin 7: *SEL
   Pin 8: Ground
   Pin 9: Terminator Power
  Pin 10: *RST
  Pin 11: *C/D
  Pin 12: *I/O
  Pin 13: Ground
  Pin 14: *Data 0
  Pin 15: *Data 2
  Pin 16: *Data 4
  Pin 17: *Data 6
  Pin 18: *Parity
  Pin 19: Ground
  Pin 20: *ATN
  Pin 21: *MSG
  Pin 22: *ACK
  Pin 23: *BSY
  Pin 24: *REQ
  Pin 25: Ground
 

External SCSI Connector (Centronics 50-Pin Female)

  Pins 1-12 and 14-25 are grounds.

  Pin 26: *Data 0
  Pin 27: *Data 1
  Pin 28: *Data 2
  Pin 29: *Data 3
  Pin 30: *Data 4
  Pin 31: *Data 5
  Pin 32: *Data 6
  Pin 33: *Data 7
  Pin 34: *Parity
  Pin 35: Ground
  Pin 36: Ground
  Pin 37: Ground
  Pin 38: Terminator Power
  Pin 39: Ground
  Pin 40: Ground
  Pin 41: *ATN
  Pin 42: Ground (Unused?)
  Pin 43: *BSY
  Pin 44: *ACK
  Pin 45: *RST
  Pin 46: *MSG
  Pin 47: *SEL
  Pin 48: *C/D
  Pin 49: *REQ
  Pin 50: *I/O
 

2.5-Inch Drive SCSI Connector (40-Pin Header)

Pins 1, 2, 39, and 40 are +5V. Pins 3, 4, 37, and 38 are ground returns for the +5V supply. Pins 5, 7, 9, 11, 13, 15, 19, 21, 23, 27, 31, and 35 are signal grounds. Pin 17 is used as a connector key and should not be present.

   Pin 6: *Data 0
   Pin 8: *Data 1
  Pin 10: *Data 2
  Pin 12: *Data 3
  Pin 14: *Data 4
  Pin 16: *Data 5
  Pin 18: *Data 6
  Pin 20: *Data 7
  Pin 22: *Parity
  Pin 24: Terminator Power
  Pin 25: *ATN
  Pin 26: *BSY
  Pin 28: *ACK
  Pin 29: *RST
  Pin 30: *MSG
  Pin 32: *SEL
  Pin 33: *I/O
  Pin 34: *C/D
  Pin 36: *REQ


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