I have no standard cookbook naswer for you, but I think you could start by looking at misc. chip producer's data sheets and application notes.
You might see for example National Semi, one possibly relevant application note is **broken link removed**
Some prcessors suport SCSI with very little extra hardware, one example is ETRAX processor from Axis. They have even a Linux version with all necessary drivers for free. See developer.axis.com for more info.
**broken link removed** does not have so enormous amount of info directly, but it shows a few application notes for some aspects of the SCSI interface.
It would be easier to help you more specific way if you would ask more specific and detailed question. In any case I hope these links help you at least a bit
Ted