Elite 23 Product Manual, Rev. A
61
9.8
Terminator requirements
ST423451N and ST423451W drives
Internal disc drive I/O termination consists of active circuits contained in an LSI module that is permanently
mounted on the PCB. All single initiator/single target (non-daisy-chain) applications require you to terminate
the initiator and drive.
Terminate both ends of the SCSI bus with ANSI SCSI-2 standard alternative 2 (active) termination. Do not mix
active and passive terminators on the same SCSI bus.
Daisy-chain configurations require you to terminate only the units at each end of the daisy chain. Do not termi-
nate any other peripherals on the chain.
Note.
Remove the Enable SCSI Terminator (TE) jumper from J4A pins 19 and 20 when terminators are not
required.
ST423451WD drives
Differential I/O Elite drives do not have provisions to add terminator sockets on the PCB. You must provide
external termination when termination is required. Terminator plugs that fit between the cable connector and
the drive connector can be purchased. See Figure 14.
9.9
Terminator power
ST423451N and ST423451W 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:
ST423451N
Pin 26
ST423451W/WD Pins 17, 18, 51, and 52
2.
Drive supplies power to the SCSI bus.
3.
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:
V TERM = 4.50 V to 5.25 V
800 mA minimum source drive capability
1.0 A maximum
ST423451WD drives
You can configure terminator power from the drive to the SCSI bus or have the host adaptor or other device
supply terminator power to the external terminator. See Section 8.1 for illustrations that show how to place
jumpers for this configuration.
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