Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Spiral Read Write Architecture for Processor Controlled Diskette Unit

IP.com Disclosure Number: IPCOM000045002D
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Billington, JT: AUTHOR [+2]

Abstract

Multiple track data transfers followed by one interrupt request are effected with a single command from an IBM Series/1 processor to a diskette unit. Heretofore, a typical operation resulting from a single command issued by the Series/1 to a Model 4966 Diskette Magazine unit, for example, allowed only a single track, single head data transfer followed by an interrupt.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Spiral Read Write Architecture for Processor Controlled Diskette Unit

Multiple track data transfers followed by one interrupt request are effected with a single command from an IBM Series/1 processor to a diskette unit. Heretofore, a typical operation resulting from a single command issued by the Series/1 to a Model 4966 Diskette Magazine unit, for example, allowed only a single track, single head data transfer followed by an interrupt.

In a representative configuration, the system may comprise a Series/1 processor with local storage, read-only storage (ROS) for control functions, and a main storage, one or more diskette units, a diskette attachment card and a power supply. The diskette unit employs common drive subassemblies for accessing the diskettes, each subassembly having read, write, and head-access capabilities. Each subassembly, among other things, may consist of a head- access mechanism, a head-load mechanism, a read/write assembly, a diskette- mounting mechanism, a diskette-drive mechanism, an electronics card, a diskette-detection circuit, and an operator handle. A typical standard diskette exchange track format is shown in the drawing.

A Spiral Read/Write procedure for diskette units allows for multiple track reads and writes. When the "Spiral" bit is on, the Spiral operation will begin with the C (cylinder), H (head), R (sector number) and N (sector size) values specified and will continue until the byte count is exhaused as long as no exception or special conditions are encountered. The manner in which the Spiral operation proceeds is as follows: For type 2 (double-sided FM recorded data) or 2D (double-sided with double-density Modified FM-MFM recorded data) diskettes, head 0 switches to head 1 on the same track or head 1 switches to head 0 on the next higher track. For type 1 diskettes (single-sided FM recorded data), only track switching will take place - head 0 will switch to head 0 on the next higher track. When the Spiral bit is off, normal operation is in effect.

For Spiral Read operations, there are a maximum of three retries per track with a maximum number of 63 retries allowed for the total Spiral operation. The figures for Seek-type operations are 5 and 5, respectively. For Write Verify operations they are 3 and 9. All Spiral retries, with the exception of Write Verify, are performed on a track basis. That is, if the spiral operation starts on C=S, H...