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 the size of program RAM used in a disk controller of a magnetic disk drive storage system, thereby efficiently reducing a work load of a microcontroller unit in the disk controller. The map allocation method is performed in a program random access memory having a 32.times.2 byte size of data storage area in the disk controller, the program random access memory being provided with the sequencer map allocation including a branch field, a next address/count field, an output field, a gate field, a field region and a data selection field. The branch field is provided with branch condition or count field enable information. The next address/count field selectively has a next address or a count value according to the branch condition. The output field is usable for testing synchronization outside the programmable control sequencer and the gate field for performing Read/Write gate control and making increase of target sector number and decrease of disk sector transmit count. The field region represents ECC/CRC block and CDR return and the data selection field is usable for comparing data from any data register with data read of the disk, thereby processing the data according to the compared result.