Time-slicing method and apparatus for disk drive

Abstract

A disk drive includes a first memory for storing microcoded program routines and sub-routines for the drive. One of the routines is a main program routine that is comprised of a plurality of service routines executable in sequence during a respective plurality of time-slots of the main program routine processing cycle. One of the service routines includes a plurality of service sub-routines executable in sequence with only one being executed during each processing cycle. The drive also includes a second memory having a register therein respectively associated with said one service routine. The register is capable of storing the addresses of locations in the first memory at which program instructions for said one service routine are stored. The drive further includes a microprocessor coupled to the first and second memories and having a program counter for supplying address signals to the first memory in order for program instructions therein to be accessed and forwarded to the microprocessor for execution, and for supplying address signals to the second memory in order for the contents of the register to be loaded into the program counter during the time-slot of said one service routine. Such contents are changed each processing cycle to the address of the first program instruction in the first memory for the servicing sub-routine next in sequence to be executed.