This is the first ATA/ATAPI standard. Released in 1994.
The standard defines the AT Attachment Interface. The standard defines an integrated bus interface between disk drives and host processors. It provides a common point of attachment for systems manufacturers, system integrators, and suppliers of intelligent peripherals.
Note: there is no practical use of this document. This is a history now.
Download: d0791r4c — ATA/ATAPI-1 (PDF)