Digital data apparatus for transferring data between a byte-wide digital data bus and a four byte-wide digital data bus

摘要

A digital data system includes a circuit for controlling data transfer between a four byte wide pathway, such as a VME bus, and a byte wide device, such as a SCSI disk drive by way of a byte wide bus (SCSI bus). The control circuit effects selective data transfer of an odd or even data byte, a data short word (two parallel bytes) or a data long word (four parallel bytes). The transfer circuit includes a four byte wide data register connected to the VME bus, four, byte wide, funnel registers connected in parallel to the data register, a byte wide FIFO memory connected between the funnel registers and the SCSI disk drive via a SCSI bus. A DMA controller and funnel controller state machine control transfer of data from the VME bus to the SCSI disk drive either as a data byte, a data short word or a data long word.