Disk controller having sequential digital logic in a state machine for transferring data between DMA device and disk drive with minimal assistance of the CPU

• US 5,721,949 A
• Filed: 05/27/1997
• Issued: 02/24/1998
• Est. Priority Date: 12/14/1993
• Status: Expired due to Term

• Current Assignee: Apple Computer Incorporated (Apple Inc.)
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Nelson, Matthew R., Smith, R. Steven
• Primary Examiner(s): Meky, Moustafa M.
• Application Number:
  US08/863,681
• Time in Patent Office: 273 Days
• Field of Search: 395/821, 395/822, 395/823, 395/825, 395/842, 395/843, 395/844, 395/894, 395/427, 395/438
• US Class Current: 710/5
• CPC Class Codes: G06F 3/0626 Reducing size or complexity of storage systems
• CPC Class Codes: G06F 3/0658 Controller construction arrangements
• CPC Class Codes: G06F 3/0676 Magnetic disk device
• CPC Class Codes: G11B 19/02 Control of operating function, e.g. switching from recording to reproducing
• CPC Class Codes: G11B 20/1252 for discontinuous data, e.g. digital information signals, computer programme data

Abstract

A method for transferring data between a host computer and peripheral storage including the steps of: (a) receiving data from the host; (b) determining if an escape command is present in the data; (c) writing the data to the a peripheral storage medium if a escape command is not present in the data; and (d) performing as least one command relative to the peripheral storage if a escape command is present in the data. Also disclosed is a method for controlling a disk drive unit including the steps of: (a) determining on a host computer a current action to be performed with a disk drive unit; (b) formatting a track of a disk engaged with a disk drive unit based upon output data provided by the host computer if the current action is a formatting action; (c) writing a sector on the disk based upon the output data provided by the host computer if the current action is a writing action; and (d) reading a sector of the disk and transferring input information to the host computer if the action is a reading action. Escape codes are used to distinguish "normal" data from "special" data. A disk drive controller of the present invention includes digital logic responsive to a data bus of the host computer and operative to develop a datatype bus based on the data bus, where the datatype bus is operative to specify one of a plurality of data types, and a converter responsive to the data bus and the datatype bus and operative to provide serial data to a disk drive unit mechanism.

Claims

1. A method for transferring data between a host and peripheral storage under the control of a state machine, said host including a central processing unit (CPU), memory means and a direct memory access (DMA) channel coupled to said memory means, said method comprising the steps of:

receiving data from said host via said DMA channel, said data being received by a state machine;

determining whether escape is enabled and whether said data includes a predetermined escape code using sequential digital logic of said state machine and with minimal assistance from said CPU of said host;

determining that an escape command is present in said data using sequential digital logic of said state machine when escape is enabled and when said data includes a predetermined escape code, and determining that an escape command is not present in said data when escape is disabled;

writing said data to a peripheral storage medium if an escape command is not present in said data under the control of said state machine; and

performing at least one command relative to said peripheral storage if an escape command is present in said data under the control of said state machine.

2. A method for transferring data as recited in claim 1 wherein said step of writing said data comprises writing said data to a magnetic peripheral storage medium.

3. A method for transferring data as recited in claim 2 wherein said magnetic peripheral storage medium comprises a magnetic disk.

4. A method for transferring data as recited in claim 1 wherein said step of performing a command comprises the steps of:

receiving additional data from said host; and

executing at least one command specified by said additional data.

5. A method for transferring data as recited in claim 4 wherein said step of executing a command comprises the steps of:

parsing said additional data into one command of a plurality of commands; and

executing said one command.

6. A method for transferring data as recited in claim 5 wherein said plurality of commands include:

a transfer data command;

a write mark command; and

a write trailer command.

7. A method for transferring data as recited in claim 6 wherein said plurality of commands further include:

an escape disabling command; and

an end data command.

8. A method for controlling a disk drive unit using a state machine comprising the steps of:

(a) determining on a host computer a current action to be performed with a disk drive unit, said host computer including a central processing unit (CPU) coupled to said state machine;

(b) formatting a track of a disk engaged with said disk drive unit based upon output data provided by said host computer if said current action is a formatting action, said step of formatting a track including the step of writing a portion of said output data to a sector on said disk, where said output data includes at least one command code preceded by an escape code, wherein said escape code and said command code are processed by sequential digital logic of a state machine located between said host computer and said disk drive unit;

(c) writing a sector on said disk based upon output data provided by said host computer via a direct memory access (DMA) channel if said current action is a writing action, a portion of said output data being written to said sector, where said output data includes at least one command code preceded by an escape code, wherein said escape code and said command code are processed by sequential digital logic of said state machine located between said host computer and said disk drive unit with minimal assistance from said CPU;

(d) reading input data from a sector of said disk and transferring said input data to said host computer via a direct memory access (DMA) channel if said action is a reading action, said transferring occurring under control of said state machine with minimal assistance from said CPU.

9. A method for controlling a disk drive unit as recited in claim 8 wherein said step of writing a sector on said disk in both said formatting action and said writing action comprises the steps of:

(a) reading a first byte of data from a direct memory access (DMA) channel of said host computer;

(b) examining said first byte to determine if it is an escape code;

(c) writing said first byte to disk if said first byte is not an escape code; and

(d) reading a second byte of data and executing a command specified by said second byte if said first byte was an escape code.

10. A method for controlling a disk drive unit as recited in claim 9 wherein said step of writing a sector further includes the steps of determining whether escape is enabled prior to examining said first byte to determine if said first byte is an escape code, and writing said first byte to disk if escape is not enabled.

11. A method for controlling a disk drive unit as recited in claim 9 wherein said second byte includes a selected command code of a plurality of command codes.

12. A method for controlling a disk drive unit as recited in claim 11 wherein if said selected command code is the same as said escape code, said selected command code is written to disk.

13. A method for controlling a disk drive unit as recited in claim 11 wherein said plurality of command codes include commands to write marks and trailers.

14. A method for controlling a disk drive unit as recited in claim 11 wherein said plurality of command codes include commands to disable escape and to end data transfer.

15. A method for controlling a disk drive unit as recited in claim 11 wherein said escape code is $99.

16. A method for controlling a disk drive unit as recited in claim 15 wherein said plurality of command codes include the following commands:

space="preserve" listing-type="tabular">______________________________________ Command Code Command Description ______________________________________ $99 Transfer data $99 (null command) $A1 Write an $A1 mark byte $C2 Write a $C2 mark byte $04 Write both CRC (trailer) bytes $0F Turn off escaping for 512 bytes $08 End data (terminate DMA transfer) ______________________________________

17. A computer system with peripheral storage comprising:

digital processing means;

scratch-pad memory means coupled to said digital processing means;

peripheral storage control means coupled to said scratch-pad memory means, said peripheral storage control means being responsive to real data and special data, said peripheral storage control means including sequential digital logic of a state machine which is operative to process escape codes contained in said real data;

peripheral storage means coupled to said peripheral storage control means such that data can be transferred between said scratch-pad memory means and said peripheral storage means under control of said peripheral storage control means with minimal assistance from said digital processing means; and

process control means operating on said digital processing means for storing data in said scratch-pad memory means, wherein said data includes both said real data and said special data, said special data being preceded by at least one escape code, wherein data derived from said real data may be written to said peripheral storage means by said peripheral storage control means, and wherein data derived from said special data may also be written to said peripheral storage by said peripheral storage control means.

18. A computer system with peripheral storage as recited in claim 17 wherein said peripheral storage means comprises a magnetic storage unit including a magnetic storage media, and wherein said process control means is operative to store data in said scratch-pad memory means including special data for said peripheral storage control means to cause said peripheral storage control means to format said magnetic media.

19. A computer system with peripheral storage as recited in claim 18 wherein data is stored on said magnetic media in a plurality of tracks, each of which is comprised of a plurality of sectors, and wherein said process control means is operative during formatting to store sufficient data in said scratch pad memory to allow said peripheral storage control means to format a track of said magnetic media.

20. A computer system with peripheral storage as recited in claim 19 wherein said process control means is further operative to read data from said scratch pad memory means which had been previously stored in said peripheral storage means.

21. A process for transferring data under control of a state machine between a host computer and a magnetic disk medium comprising the steps of:

detecting the existence of a disk command originated by said host computer, said host computer including a central processing unit (CPU) coupled to said state machine;

upon the detection of a format disk command, calculating and storing format data to scratch-pad memory and subsequently using said format data to format a track on said disk utilizing sequential digital logic of said state machine to format said track;

upon the detection of a write disk command, calculating and storing write data to said scratch pad memory comprising a data header information, a number of bytes of real data, and trailer information, and subsequently using the write data stored in said scratch pad memory to write a sector on said disk, utilizing sequential digital logic of said state machine to write said sector with minimal assistance from said CPU; and

upon the detection of a read disk command, transferring a sector of read data from said disk to said scratch pad memory utilizing sequential digital logic of said state machine with minimal assistance from said CPU.

22. A process for transferring data as recited in claim 21 wherein said calculation and storage of format data and said calculation and storage of write data includes the storage of special data preceded by an escape code.

23. A disk drive controller comprising:

sequential digital logic in a state machine responsive to a data bus and other inputs of a host computer, said host computer including a central processing unit (CPU) and a direct memory access (DMA) device, said sequential digital logic being operative to develop a datatype bus based upon data on said data bus and said other inputs, where said datatype bus specifies one of a plurality of data types, said sequential digital logic being operative to process an escape code present on said data bus such that said sequential digital logic serves to assist in controlling a disk drive unit mechanism with minimal assistance from said CPU, said sequential digital logic being further operative to transfer data between said DMA device and said disk drive unit mechanism with minimal assistance from said CPU;

a register for combining said data bus and said datatype bus into an expanded bus such that said expanded bus includes said data bus and said datatype bus in parallel; and

converter means responsive to said expanded bus, such that said expanded bus serves as an input to said converter means, said converter means being operative to provide serial data developed from said expanded bus to said disk drive unit mechanism.

24. A disk drive controller as recited in claim 23 wherein said converter means comprises an MFM converter.

25. A disk drive controller as recited in claim 23 wherein said sequential digital logic includes:

means for detecting whether an escape code is present in said data on said data bus; and

means for performing one of a plurality of commands in response to the detection of an escape code.

26. A disk drive controller as recited in claim 25 wherein at least one of said commands controls the data present on said datatype bus.

27. A disk drive controller as recited in claim 25 wherein said data types include Normal, Mark, and CRC data types.

28. A disk drive controller as recited in claim 27 wherein said data types include the following:

space="preserve" listing-type="tabular">______________________________________ Data Type Code Date Type Description ______________________________________ 00 Normal Data 01 Mark Data 10 CRC Data 11 Indeterminate ______________________________________

29. A disk drive controller as recited in claim 25 wherein said plurality of commands comprises:

a transfer data command;

a write a mark byte command; and

a write a trailer byte (CRC) command.

30. A disk drive controller as recited in claim 29 wherein said plurality of commands further comprise:

an escape disabling command; and

an end data command.

31. A disk drive controller as recited in claim 25 wherein said escape code is $99.

32. A disk drive controller as recited in claim 31 wherein said plurality of command codes include the following commands:

space="preserve" listing-type="tabular">______________________________________ Command Code Command Description ______________________________________ $99 Transfer data $99 (null command) $A1 Write an $A1 mark byte $C2 Write a $C2 mark byte $04 Write both CRC (trailer) bytes $0F Turn off escaping for 512 bytes $08 End data (terminate DMA transfer) ______________________________________