HP Surestore 5200ex series Optical Disk Drives - Manual (Page 61)

Appendix B B-5
Operating This Drive on a SCSI Bus
A Brief Overview of SCSI
Oper
ati
n
g th
e Drive
o
n
a
SC
SI
Bu
s
The differential bus uses two lines for each signal and measures the voltage
difference between the two signals. Differential retains more signal quality than
single-ended and is not as sensitive to noise, allowing for a longer cable length. The
maximum allowable length of a differential bus is 25 meters (82 feet) for all types
buses (narrow, wide, fast, Fast-20).
Connectors
Narrow devices (50-pin) use the following connectors:
• 50-pin low-density clip Centronics-type (external)
This is a large connector that is similar to a printer cable. This type of connector
is gradually being replaced by the Micro D connector, described below.
• 50-pin high density Micro D (using thumbscrews or small clips) (external)
• This connector is similar to a D-type connector, but smaller and with smaller pin
holes placed closer together.
• 50-pin low-density ribbon (usually internal to the host)
Wide devices (68- pin) use the following connectors:
• 68-pin high density Micro D connector (external)
This connector is similar to a D-type connector, but longer and slimmer and with
smaller pin holes placed closer together. This connector is becoming the most
common.
• 68-pin high density ribbon (usually internal to the host)
NOTE For more complete information on the theory and operation of the SCSI bus, you
may want to go to:
Adaptec - major supplier in SCSI buses
www.adaptec.com
Symbios Logic - Working drafts of SCSI specifications
www.symbios.com/x3t10