Browse Prior Art Database

Data Parity Checking on ESDI Disk Controllers

IP.com Disclosure Number: IPCOM000035280D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Dixon, JD: AUTHOR [+2]

Abstract

This article describes a method by which parity checking can be performed on enhanced small device interface (ESDI) disk controllers when using media writing chips which do not support parity generation or checking of data. (Image Omitted)

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
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Data Parity Checking on ESDI Disk Controllers

This article describes a method by which parity checking can be performed on enhanced small device interface (ESDI) disk controllers when using media writing chips which do not support parity generation or checking of data.

(Image Omitted)

In some personal computers (PCs) there is no method for performing data validity checking on customer data through the ESDI media writer chip which generates the ESDI serial data stream. This is because the chip does not support parity checking of the customer data that flows through it to the ESDI disk drives to which it is attached. A method is disclosed herein which allows this to be accomplished. This method allows the data which passes through the ESDI media writer to be verified on both read and write operations and allows parity propagation through the remainder of the ESDI controller card to the host main memory.

An ESDI controller card is a device which allows the access of computer data which is stored on an ESDI interface disk drive by a host computer system. This computer data is stored as a serial data stream in blocks called sectors. Each sector contains 512 bytes of computer data. Error corection code (ECC) and addressing control bytes are also present in each sector which allow the ESDI media writer to identify each block uniquely and check the data within the block for errors.

Even ECC characters are present on the drive data sectors to insure the validity of the data which is written on the drive, there is no way to check the data for validity once it is read into the media writer chip. This is because current media writer chips do not incorporate data parity generation or checking in their designs. Because of this, data errors which could occur within the chip or associated peripheral circuitry during a read or write operation may go undetected.

The technique of this disclosure provides for parity generation and checking of data as it passes through an ESDI media writer chip. It does this by using a very large-scale integration (VLSI) chip in parallel with the ESDI media writer. This VLSI chip which is referred to as the DATACHK chip herein monitors the data which is passing through the media writer chip and checks the data for validity. The DATACHK chip checks this data by one of two means, depending on whether the data is being written to the ESDI disk drive or being read from the ESDI disk drive.

Fig. 1 is a flow chart illustrating parity checking for write data. When data is being written to the ESDI disk drive, the DATACHK chip is initialized by the ESDI card microcontroller to set write check mode, the number of data bytes which are in the sector of data, and the data address mark character. When the DATACHK chip is initialized, it looks at the INDEX and SECTOR tags which are input to the ESDI media writer chip to synchronize itself to the ESDI data stream. When it sees a negative transition on either INDEX or SECTOR, it know...