Seagate HAWK 4 Series Product Manual page 71

Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. E
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11.6.4.3 Terminator requirements
Internal disc drive I/O termination (provided only in single ended I/O model ST15230W drives) consists of
active circuits in an LSI module that is permanently mounted on the PCB. All single initiator/single target
(nondaisychain) applications require that the Initiator and disc drive be terminated. Daisy-chain applications
require that only the units at each end of the daisy-chain be terminated. All other peripherals on the chain
must not be terminated. (See Figure 11.6.3-2).
Note. Remove drive terminator enabling jumper TE (see Figure 10.1-1) where terminators are not required.
Removal of terminator power source selection jumper TP (see Figure 10.1-1) does not disconnect
the terminator resistors from the circuit.
It is highly recommended that ANSI SCSI-2 Standard's Alternative 2 termination (active termination) be used
for single-ended ST15230W and ST15230WC applications, especially if the bus will be operated at transfer
rates above 5 Mbytes/sec. The ST15230W provides on-board active termination that can be disabled by
removal of the enable jumper TE (see Figure 10.1-1).
Note. Active terminators are highly recommended for use in the daisy-chain as described above. Active
and passive terminators should not be mixed on the same SCSI bus.
Differential I/O ST15230WD does not have terminators on the PCB. The user, systems integrator or host
equipment manufacturer must provide a terminator arrangement external to the drive. Models ST15230WC
and ST15230DC do not have terminators on the drive PCB and there is no provision for terminator power in
the 80 pin I/O connector.
11.6.4.4 Terminator power
The "W/WD" model drives may be configured to accept terminator power from drive connector pins 17, 18, 51
and 52 of the SCSI Bus, to supply power to the SCSI bus or to provide terminator power for internal termina-
tion circuits from the drive power connector. See Figures 10.1-1 and 11.6-1. The drive can provide power
both to its own terminators and to the SCSI Bus terminators at the other end of the I/O cable if both "TP"
jumpers are on (models ST15230W/WD only).
SCSI devices providing terminator power (TERMPWR)* shall have the following characteristics:
The "WC" and "DC" model drives cannot furnish terminator power, because no conductors in the 80 pin I/O
cable are devoted to terminator power.
*See Figure 10.1-1 for configuration details.
V TERM = 4.50 V to 5.25 V
800 mA min source drive capability
1.0 A maximum
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