Set FID

Writing the FID to drive's register F takes a simple I/O write cycle. The drive circuitry senses that write operation and displays its content in Hex in the FID seven-segment display.

This mechanism has been conceived for advanced applications working with multiple files. The operator places tapes on drives arbitrarily. Software reads LABELs obtaining the FID and maps those to drive IDs. Then, Software writes each FID to the corresponding drive's register F so the Operator can know which file has been mounted in which drive.