Motorola MPMC101 user manual Introduction

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Introduction

All SCSI devices are required to operate using asynchronous data transfers. Synchronous transfers are optional, and negotiated between the host and target during power-up.

There are two electrical alternatives, single-ended and differential. They are electronically incompatible and can not be mixed on the same physical bus. Cable lengths up to 25 meters can be used for differential systems. Single-ended configurations can be up to 6 meters. The overall performance of the two is about the same.

Shielded and non-shielded cabling can be mixed on the same bus; however, the non-shielded connections should be restricted to internal cabinet applications only. All SCSI devices are configured with a socket connector. The bus cable consists of the mating pin-type connectors.

Both ends of the bus cable must be properly terminated. Interface errors can be reduced if the termination voltage is maintained at the extreme ends of the cable. All SCSI hardware include a setting (usually with hardware jumpers) that allows the device to serve as a terminator. Where possible, the SCSI devices serving as initiators should supply terminator voltage; which again, is usually a hardware jumper on the deviceÕs SCSI adapter or controller card.

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