Programmable control sequencer of disk controller and method for map

Abstract

An improved programmable control sequencer and a method for its map allocation capable of reducing a size of program RAM in a disk controller, of a magnetic disk drive storage system. The programmable control sequencer includes a program random access memory (RAM) having a 16.times.7 bit size of storage area, provided with a branch/data selection field, an encoded next address/count field and an output field. The branch/data selection field has either one of a branch condition or count field enable information and selects a given data register to compare data read out from a disk with data of the selected data register. The encoded next address/count field has an encoded value of either a next address or a count value according to the branch condition. The output field is used for testing a synchronization outside of said programmable control sequencer. An address generator generates an address for accessing the program random access memory in accordance with the information of the branch/data selection field and the encoded next address/count field. A decoder decodes the encoded next address/count value to provide the decoded information to the address generator. A decoder selection decoder decodes the information of the branch/data selection field.