6.2. Terminator requirements

This section defines the requirements of the terminator and terminator power. Section 7 defines the location of terminators in system configurations.

All terminators in PnP SCSI systems shall conform to the terminator requirements in the SCSI-3 Parallel Interface document. The terminators shall operate correctly over a TERMPWR voltage range of 4.0-5.25 Vdc. Regulated terminators are required. These are often referred to as alternative 2 or active terminators.

The host and the peripheral sub-system shall provide terminator power (TERMPWR) to the SCSI bus. All terminators must be powered from the TERMPWR line(s) in the SCSI bus.

Note Exceptions may be necessary for battery operated devices and PCMCIA PC-Cards.

Devices providing TERMPWR must provide a self-resetting device (e.g. positive-temperature-coefficient or circuit breaker device) to limit the maximum amount of current sourced instead of a fuse. Such a device opens the circuit when excessive current is drawn and closes the circuit when the device resets.