Specifications

2.5 SCSI INTERFACE - J7
The SCSI interface (17) uses a 5O-pin male header connector to interface with SCSI compati-
ble peripherals. Table 2-22 shows the pinout and signal defmitions of this interface. Refer to
your
SCSI device documentation, or the ANSI X3.131 SCSI specification (referred to in
Chapter 4) for detailed information on the signal functions. Be sure that the maximum total
SCSI bus cable length, from the board's connector to the most distant SCSI peripheral, does
not exceed
18 feet, and that the SCSI bus is properly terminated at both ends.
Note
If the SCSI interface is not needed, you should disable it
by placing a shorting block on pins 1 and 2 of the SCSI
connector (J7). When the shorting block is in place. the
system bypasses any attempt to boot from the SCSI device.
which can speed up the boot process.
Table 2-22. SCSI Interface Connector (J7)
PIN SIGNAL
FUNCTION
1
• 49
(All odd pins) Signal grounds
2 -DBO
o ta B·t 0 (LSB)
4 -DB1 1
6
-DB2
2
8
-DB3
3
10
-DB4
4
12
-DB5
5
14
-DB6
6
16 -DB7
I I
7 (MSB)
18 -DBP
Data Parity
20,22,24 GrOl.l'ld Signal Ground
25
---
(Not used)
26 TERMPWR Termination +5VDC
28,30
GrOl.l'ld Signal Ground
32
-ATN
Attention
34 GrOl.l'ld
Signa l GrOl.l'ld
36 -BSY Busy
38
-AtK Transfer Acknowledge
40
-RST
Reset
42
-MSG Message
44 -SEL
Select
46 -C/O
Control/Data
48
REQ
Transfer Request
50 -I/O
Data direction
2-21