Seagate ST12450W, Product Manual

Page: 68 / 84

58 ST12450W/WD Product Manual, Rev. A
11.7.3.3 Terminator requirements
ST12450W
Internal disc drive I/O termination consists of active circuits contained in
permanently mounted IC terminator packs on the main PCB. All single
initiator/single target (non-daisy-chain) applications require you to terminate
the initiator and drive.
You must terminate both ends of the SCSI bus with ANSI SCSI-2 standard
alternative 2 (active) termination, especially if the bus operates at fast SCSI
transfer rates.
Daisy-chain configurations require you to terminate only the units at each
end of the daisy chain. Do not terminate any other peripheral on the chain.
Note. Remove the Enable Drive Terminator jumper on J4 pins 11 and 12
when terminators are not required.
ST12450WD
Differential I/O Barracuda drives do not have provisions to add terminator
sockets on the PCB. You must provide external termination.
11.7.3.4 Terminator power
The drive may be configured to accept terminator power using pins 51 and
52 of the SCSI bus to supply power to the SCSI bus or to provide terminator
power for optional internal termination resistors using the drive’s power
connector (see Figure 14). The drive can provide power both to its own
terminators and to the SCSI bus terminator power line.
SCSI devices providing terminator power (TERMPWR) must have the
following characteristics:
• V TERM = 4.50V to 5.25V
• 800 mA minimum source drive capability
• 1.0A maximum