Seagate Elite 9, Product Manual

Page: 64 / 82

54 Elite 9 Product Manual, Rev. C
11.7.1 Physical characteristics
This section defines the connectors, cables, signals, and terminators needed
to implement the SCSI interface.
11.7.1.1 Physical description
You can daisy chain multiple SCSI devices on a common cable if each device
has the same type of driver and receiver (all single-ended or all differential).
Devices having single-ended interface circuits cannot be on the same daisy
chain with devices having a differential interface circuit. Both ends of the
cable must be terminated. All signals are common between SCSI devices.
A maximum of 8 SCSI devices (including the host) may be daisy chained
together when using a non-wide bus and ST410800N/ND drives. A maxi-
mum of 16 SCSI devices (including the host) may be daisy chained together
when using a wide bus and ST410800W/WD drives.
Terminate both ends of the daisy chain, but do not terminate any inter-
mediate SCSI device. The ST410800N/W drives are equipped with perma-
nently mounted IC terminators, which you can turn on or off using the
Terminator Enable jumper on pins 19 and 20 of J4A. The differential
(ST410800ND/WD) drives have removable on-board terminators.
11.7.1.2 Cable requirements
Sections 11.7.1.2.1, 11.7.1.2.2, and 11.7.1.2.3 describe the single-ended,
differential, and general cable requirements for Elite 9 drives.
11.7.1.2.1 Single-ended I/O circuits
The maximum total cable length for use with drives having single-ended I/O
driver and receiver circuits is 6 meters (19.7 feet) when operating at line data
transfer rates of 5 Mbytes/second or less, and 3 meters (9.85 feet) when
operating at transfer rates greater than 5 Mbytes/second (fast SCSI). A stub
length of no more than 0.1 meter (0.33 feet) is allowed off the mainline
interconnection with any connected equipment. An ideal impedance match
with cable terminators implies a cable characteristic impedance of 132 ohms.
Single-ended I/O cable pin assignments for ST410800N drives are shown in
Table 10. Single-ended I/O cable pin assignments for ST410800W drives are
shown in Table 12.
11.7.1.2.2 Differential I/O circuits
The maximum total cable length for use with drives having differential I/O
drivers and receiver circuits is 25 meters (82 feet). A stub length of no more
than 0.2 meter (0.66 foot) is allowed off the mainline interconnection with
any connected equipment. An ideal impedance match with cable termina-
tors implies a cable characteristic impedance of 122 ohms. Differential I/O
cable pin assignments for ST410800ND drives are shown in Table 11.
Differential I/O cable pin assignments for ST410800WD drives are shown in
Table 13.