| EXTERNAL
SCSI TERMINATORS |
- SCSI Terminators
- Two
terminators are needed to terminate a SCSI chain, one at
each end. SCSI adapter cards have built-in terminators leaving
the last peripheral on the chain to be terminated. For non-Differential
SCSI which covers the majority of cases, the following are
recommended:
-
Use Passive SCSI terminator if total chain distance
is less than 6ft, and I/O speed is 10Mbps or less. Passive
terminator sits on the bus to minimize reflections at the
end of the cable and simply provides an impedance that’s
close to the impedance of the cable.
-
Use Active SCSI terminator if SCSI II and III devices
are used, and total length of the chain is 20ft or less.
Active SCSI terminator prevents signal reflections to provide
data integrity and works to control the impedance at the
end of the bus by using a voltage regulator, not just the
power supplied by the SCSI controller. It is more reliable
than passive termination for high speed devices and long
distance applications.
-
Use Forced Perfect Terminator (FPT) if total distance
is more than 20ft, more than 5 devices are chained, and
when passive or active terminators cannot do the job. FPT
terminator goes beyond stabilizing the power applied to
the terminator by altering its impedance to actively compensate
for variations among many different cables and devices by
means of diode switching and biasing. It has built-in troubleshooting
LEDs.
-
Use Differential Terminator
only for SCSI systems that use the Differential
SCSI bus, also known as High Voltage Differential (HVD).
Use Low Voltage Differential (LVD) Terminator for
Ultra2, Ultra160, & Ultra320 Drives.
|
|
External
|
SCSI I
|
SCSI II
|
SCSI III
|
UltraSCSI
|
|
PC/Mac Connector
(Standard Pin-Out)
|
|
HPDB50
HPCen50 |
HPDB68 |
VHDCen68
|
|
IBM RS/6000
(Unique Pin-Out)
|
HPCen60 |
HPCen60 |
HPCen68 |
HPCen68 |
|
IBM PS/2
(Unique Pin-Out)
|
DB25 |
|
|
|
|
Internal SCSI
(Standard Pin-Out)
|
IDC50 |
HPDB50 |
HPDB68 |
HPDB68 |
|
SCSI Ultra320 VHDCen68 LVD/SE/Differential External Terminator 
UltraSCSI HPDB68 Active External Terminator 
UltraSCSI HPDB68 Passive External Terminator 
SCSI HPDB50 Active External Terminator 
SCSI HPDB50 Differential External Terminator 
SCSI HPDB50 Passive External Terminator 
SCSI Cen50 Male Active External Terminator 
SCSI Cen50 Male Passive External Terminator 
SCSI Cen50 Male FPT External Terminator with Built-in Tester 
SCSI Ultra320 HPDB68/VHDCen68 Terminator with VHDCen68 External Port 
SCSI Cen50 Male Passive Pass-Thru External Terminator 
SCSI Cen50 to HPDB68 with High Byte Active Termination 
SCSI HPDB50 to HPDB68 with High Byte Termination 
SCSI IDC50 to HPDB68 with High Byte Active Termination 
