In response to the mounting of a magnetic tape on the tape drive, the tape drive begins reading data from the tape into the preload buffer while concurrently signalling the data processor that the tape drive is instantaneously available to read/write data. The data processor can then begin the data transfer...http://www.google.co.uk/patents/US5487171?utm_source=gb-gplus-sharePatent US5487171 - System for reading and stopping reading data from magnetic tape into memory in response to mount command and write command respectively from the system processor
