Adaptec 1742A User Manual

Contents

Standard ModeThe operation mode that allows software written for the AHA-1540/1640 family to be fully compatible with the AHA-1740A/1742A/1744. The limitation is that you cannot selectaddresses beyond 16 MBytes or access several EISA registers.Synchronous Data TransferA method of data transfer on the SCSI bus involving clockingdata on to the bus with a fixed-length fixed-frequency strobepulses. The acknowledgments may be delayed several clock peri-ods from the data requests. Synchronous data transfer can beused only for data transmission on the SCSI bus. It is prohibitedfor command, message, and status transmission.Synchronous Data Transfer NegotiationThe message exchange between the initiator and the target thatallows the negotiation of the data transfer frequency and delaybetween requests and acknowledgments required for synchronousdata transfer. Once negotiated, synchronous data transfer pa-rameters remain unchanged until certain reinitialization activi-ties occur.Tagged QueuingA SCSI-2 feature that allows the SCSI device to return data in adifferent order than requested by the SCSI host adapter.TargetA SCSI device that performs an operation requested by an initia-tor. The target may be a peripheral device performing a servicefor an initiator. The target may also be a host adapter performinga processor-type device service for an initiator.WordA 2-byte (16-bit) unit of data.Zero Latency ReadsA Method of minimizing mechanical limitations of fixed disk by re-questing data in an unordered sequence. The data is reorderedby the host adapter.padaptec AHA-1740A/1742A/1744GL-8