Seagate Technology Incorporated

Seagate Technologies, Inc.

Marvin Mang-Yin Lum

Sean R Atsatt

Prafulla Bollampalli Reddy

John Chester Masiewicz

Don M Robinson

Kathleen Anne Duncan

Pervez Edul Virjee

Translating between physical and logical (or virtual) address spaces occurs autonomously using information decoded by an address mode translator from command bits within a host CPU issued command. The translator communicates with a hard disc controller unit local microprocessor or microcontroller and controller unit task registers. A host CPU issued command interrupts the local microprocessor and activates the address mode translator by writing to an appropriate controller unit task register using indirect addressing. The address mode translator preferably provides four algorithms, with algorithm selection occurring autonomously according to the decoded command bits. The algorithms provide physical block address to physical CHS cylinder-head-sector conversion, logical CHS to logical block address conversion, and also provide divide and multiply functions, useful for disc caching. Upon completion of the conversion or other function procedure, the address translator signals that the processed result is ready for reading by the controller unit local microprocessor or microcontroller. The translator may be implemented as a microprogrammed sequencer with an instruction set tailored to perform linear address translations and stored in memory associated with the local microprocessor. Alternatively, the instruction set may be downloaded by the microprocessor from disc drive software. The address translator provides the microprocessor with a translated address in a usable form more rapidly than if the local microprocessor had made the translation.

Autonomous high speed linear space address mode translation for use with

A disc controller services a host 'read' command, without intervention by the disc controller's microcontroller, if the requested data is found in the disc controller's cache. The disc controller stores at least one cache entry. Each cache entry includes an address, a logical Bit, a valid Bit and a set of four buffer parameters: upper limit address, base address, pointer to the sector count and sector count. Each host command is decoded by the disc controller, and if the command is a 'read' command the address in the cache entry is compared against the address in the host command. If the addresses match and the cache entry address is marked as being valid by its Valid bit, a 'cache hit' signal is generated and the disc controller starts transferring the data requested by the host without waiting for the disc controller's microprocessor to process the host command. In particular, a sequencer and data transfer circuitry automatically generate a host interrupt request signal and transfer to the host at least a subset of the requested set of data blocks specified by each read command when a cache hit signal is generated. The disc controller includes circuitry for updating the information stored in the cache entry so that said updated information stored in the cache entry identifies data blocks in the cache sequentially subsequent to those data blocks transferred to the host.

Disc drive controller with apparatus and method for automatic transfer

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San Jose, CA, United States of America

Marvin Mang-Yin Lum