Dell Precision 420 - Manual (Page 71)

External SCSI Connector
The 68-pin external small computer system interface (SCSI) connector on the system back panel supports external Ultra SCSI devices such as
scanners, zip drives, and optical drives.
If you reconfigure your hardware, you may need pin number and signal information for the external SCSI connector. Figure 6 illustrates the pin
numbers for the external SCSI connector, and Table 5 lists and defines the pin assignments and interface signals for the external SCSI connector.
Figure 6. Pin Numbers for the External SCSI Connector
Table 5. Pin Assignments and Interface Signals for the External SCSI Connector
11 BUSY I Busy
12 PE I Paper end
13 SLCT I Select
14 AFD# O Automatic feed
15 ERR# I Error
16 INIT# O Initialize printer
17 SLIN# O Select in
18-25 GND N/A Signal ground
Pin Signal I/O Definition
1-16 GND N/A Signal ground
17-18 TRMPWR N/A Terminator power
19 RSVD N/A Reserved
20-34 GND N/A Signal ground
35 D12 I/O SCSI data bit 12
36 D13 I/O SCSI data bit 13
37 D14 I/O SCSI data bit 14
38 D15 I/O SCSI data bit 15
39 DPARH I/O SCSI data parity high
40 D0 I/O SCSI data bit 0
41 D1 I/O SCSI data bit 1
42 D2 I/O SCSI data bit 2
43 D3 I/O SCSI data bit 3
44 D4 I/O SCSI data bit 4
45 D5 I/O SCSI data bit 5
46 D6 I/O SCSI data bit 6
47 D7 I/O SCSI data bit 7
48 DPARL I/O SCSI data parity low
49-50 GND N/A Signal ground
51-52 TRMPWR N/A Terminator power
53 RSVD N/A Reserved
54 GND N/A Signal ground
55 ATN I/O SCSI attention
56 GND N/A Signal ground