Emulex MD21/S2, Technical Manual

Page: 43 / 88

MD21 Controller Setup
5.3.1.5 SCSI Bus Parity Enable (SWl-8)
Switch (SWl-8) enables the SCSI bus parity check. The factory
setting for this switch is OFF (parity check disabled), as shown in
Figure 5-5.
0
N
t
1 2 3 4 5 6 7 8
■
0
N
t
1 2 3 4 5 6 7 8
f l
Parity check disabled
(Factory setting)
Parity check enabled
Figure 5-5. Parity Enable Switch Setting
5.3.2 SCSI BUS TERMINATION POWER OPTION
The SCSI termination power option allows the MD21 to supply between
+4 and +5 VDC power to the subsystem^ external terminators via pin
26 of the SCSI bus. The SCSI Termination Power option is not
required if the MD21 is resident in an Emulex subsystem that
contains an internal terminator power board. On-board terminators
(see subsection 5.3.3) do not require that the SCSI Termination
Power option be installed.
C A U T I O N
When this option is implemented, the voltage
supplied on pin 26 is not current limited. If this
pin becomes grounded— for example, by a misoriented
connector— damage to the MD21 Controller and/or to
the system cabling may result.
If the SCSI termination Power option is required, install a #1N5817
diode at reference designator CR2. Also connect a wire-wrap jumper
between jumper posts E and F. See Figure 5-1.
Installation 5-7