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Hawk 4XL Product Manual, Rev. A
9.8
Terminator requirements
Internal disc drive I/O termination consists of active circuits in an LSI module that is permanently mounted on
the PCB. All single initiator/single target (non-daisy-chain) 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 termi-
nated. All other peripherals on the chain must not be terminated. (See Figure 15).
Note.
Remove drive terminator enabling jumper TE where terminators are not required. Removal of termina-
tor power source selection jumper TP (see Figure 11) 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 applications with single-ended, especially if the bus will be operated at transfer rates above 5 Mbytes/sec.
The “N” and “W” models provide on-board active termination that can be disabled by removal of the enable
jumper TE (see Figure 11).
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.
9.9
Terminator power
“N” and “W” model drives
You can configure terminator power in four different ways. See Section 8.1 for illustrations that show how to
place jumpers enabling each of the following terminator power configurations:
1.
Drive accepts terminator power through SCSI bus pins:
“N” models
Pin 26
“W” models
Pins 17, 18, 51, and 52
2.
Drive supplies power to the SCSI bus.
3.
Drive provides terminator power for optional internal terminator resistors using the drive’s power connector.
4.
Drive provides power to its own terminators and to the SCSI bus terminator power line.
SCSI devices providing terminator power (TERMPWR) must have the following characteristics:
8-bit SCSI
V TERM = 4.25 V to 5.25 V
800 mA minimum source drive capability
1.0 A maximum
16-bit SCSI
V TERM = 4.25 V to 5.25 V
1,500 mA minimum source drive capability
3.0 A maximum
