Electrical computers and digital processing systems: memory – Addressing combined with specific memory configuration or... – Dynamic-type storage device
Utility Patent
1998-03-31
2001-01-02
Chan, Eddie P. (Department: 2751)
Electrical computers and digital processing systems: memory
Addressing combined with specific memory configuration or...
Dynamic-type storage device
C711S200000, C710S024000, C710S026000, C712S224000
Utility Patent
active
06170034
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to data transfer and more particularly to data transfer of selected data intermixed with other data.
BACKGROUND OF THE INVENTION
There exist some computer applications that use at least two types of data that are stored intermixedly or non-contiguously. For example, audio and video data may be stored in the same file on a hard drive. The file occupies a certain amount of data units, such as sectors, on the storage media of the hard drive. Thus, those sectors contain either audio or video data. Those applications can desire that only one type of data, e.g., video, is transferred.
There exist commands that provide information so that only the desired data type is transferred. This command provides mask information which selects which type of data is to be transferred. Typically, this masked transfer is performed by firmware. Unfortunately, the firmware not only increases system overhead by utilizing microprocessor resources, it also requires precious storage space.
To illustrate, a data controller of a hard drive is coupled to a SCSI bus, a microcontroller, RAM, ROM and the storage medium. The mask information is received by the data controller. Via firmware processing, the microcontroller processes the mask information thereby using valuable microcontroller resources. The firmware must be stored in the ROM, thus using up memory space at an additional cost. Furthermore, present hardware requirements demand faster data transfer between the storage medium and the SCSI bus. The firmware implementation does not readily lend itself to this demand since microcontroller intervention is required, as well as the access time to the ROM to fetch the firmware.
A need exists, therefore, for an implementation that provides a masked data transfer without adding significantly to system overhead. The present invention meets this need.
SUMMARY OF THE INVENTION
The present invention includes a method of transferring data that are not masked. A request is made to provide a masked data transfer. The requester transmits mask information, which is then stored in word-sized sections as a transfer mask table. The mask information is duplicated and also stored in an interleaved manner with the original mask information. Each bit of the mask information is associated to a specific sector address or other data unit address. Each bit of the mask information is compared to its corresponding duplicate bit. An error signal is generated if those bits do not match. The mask table is parsed to effectuate the transfer.
The transfer mask table can be indexed by initializing a mask index counter and a mask bit counter (both counters are programmable). The counters can be considered as storage devices that store, save or maintain values. The mask index counter sets the address of an entry to be first acquired. The mask bit counter sets which bit of the word to first evaluate, i.e., whether certain data is masked. After the first entry is acquired, the mask bit counter starts the next mask word preferably at bit zero. The mask index counter is appended to a mask base address register to form a complete mask buffer address.
After an entire word of sectors is transferred, i.e., each sector that corresponds to a bit of the word is transferred, the next word (if necessary) is fetched. The present invention has nearly all of the time that the last sector of the word is transferred to fetch and load the next word into the mask bit and mask index counters. Thus, the present invention in effect pipelines the mask word fetches to provide continuous data transfer. Furthermore, the counters maintain their respective values so that if the sectors to be transferred are-not contiguous (on the same track), the counters do not have to be reprogrammed at the completion of a track seek.
The present invention also has the capability not to transfer the last requested sector if that sector is masked. This capability eliminates the need to parse the mask table to determine how a data formatter should be programmed. The present invention evaluates whether a stop count value equals a stop threshold value when a sector is identified as being masked. The stop count value is incremented for each sector that is read from the first storage device, regardless of whether that sector is to be transferred or masked. The stop threshold value is the total number of sectors to be transferred and masked. If the stop count value equals the stop threshold value and the sector is masked, a flag is generated to stop the transfer of that last masked sector.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings in which details of the invention are fully and completely disclosed as a part of this specification.
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Hanna Stephen D.
Springberg David M.
Weston-Lewis Graeme
Chan Eddie P.
Encarnacion Yamir
LSI Logic Corporation
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