Programmable data transfer without sector pulses in a headerless disk

Abstract

A disk controller for headerless disk drive system contains an EOS counter which increments each time a read/write head passes a servo sector. Control words in a data buffer of the disk drive system and event-counts in registers of the disk controller indicate sizes and relative positions of frame fields between the servo sectors. The disk controller decodes control words from a data buffer to determine which fields are in the data frames and determine event-counts for the frame fields. The position of read/write heads in a data frame is then determined by counting pulses of a read or write clock where counting to an event-count identifies a boundary of a frame field. The disk controller synchronizes with the media at EOS pulses and data synchronization fields and otherwise relies on the event-counts and the read or write clock signal. No sector pulses are required because data segments are identified by timing relative to EOS pulses. Assertion of a read gate during a read can be delayed to ensure that variation in the timing of assertion and detection of EOS pulses does not cause a read gate to be asserted before the read/write head reach a data segment.