Fault tolerant comparator for disk drive controllers

A comparator for comparing disk data to a synchronization pattern, comprising:

• a plurality of exclusive NOR gates for exclusive NORing the disk data with the synchronization pattern to form an exclusive NOR output pattern;
• a left boundary stage for locating a left boundary of an error burst in the exclusive NOR output pattern and for generating a left boundary output pattern which indicates the position of the left boundary of the error burst;
• a multiplexer for realigning the exclusive NOR output pattern by a number of bits equal to a maximum allowable error burst width to form a multiplexer output pattern, the exclusive NOR output pattern being realigned such that the least significant bits are shifted in a direction towards the most significant bits;
• a plurality of OR gates for ORing the left boundary output pattern with the multiplexer output pattern to form an OR gate output pattern;
• and
• an AND stage for ANDing together all of the bits of the OR gate output pattern.

A method of comparing disk data to a synchronization pattern, comprising the steps of:

• exclusive NORing the disk data with the synchronization pattern to form an exclusive NOR output pattern;
• locating a left boundary of an error burst in the exclusive NOR output pattern and generating a left boundary output pattern which indicates the position of the left boundary of the error burst;
• realigning the exclusive NOR output pattern by a number of bits equal to a maximum allowable error burst width to form a realigned exclusive NOR output pattern, the exclusive NOR output pattern being realigned such that the least significant bits are shifted in a direction towards the most significant bits;
• ORing the left boundary output pattern with the realigned exclusive NOR output pattern to form an OR output pattern;
• and
• ANDing together all of the bits of the OR output pattern.