Browse Prior Art Database

Automatic Initial Microprogram Load of Writable Control Storage

IP.com Disclosure Number: IPCOM000081370D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 74K

Publishing Venue

IBM

Related People

Recupero, AA: AUTHOR [+3]

Abstract

The introduction of control units and central processing units using a volatile writable control storage for the control microprogram, has made necessary an automatic reload of the control microprogram every time the device is powered up. An inexpensive nonvolatile storage device must be used to retain the control microprogram to be stored. Herein described is the process of automatically loading a writable control storage, during the power-up of a microprogrammed control unit or processing unit.

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

Automatic Initial Microprogram Load of Writable Control Storage

The introduction of control units and central processing units using a volatile writable control storage for the control microprogram, has made necessary an automatic reload of the control microprogram every time the device is powered up. An inexpensive nonvolatile storage device must be used to retain the control microprogram to be stored. Herein described is the process of automatically loading a writable control storage, during the power-up of a microprogrammed control unit or processing unit.

The storage device is activated automatically by turning on system power. Data then is transferred from this device to the writable control storage. Upon termination of the IMPL (Initial Microprogram Load), the control microprogram must automatically be initialized and started. In addition, IMPL can be initiated manually for maintenance purposes. Diagnostic microprograms may also be kept stored in the nonvolatile storage device, for transfer to the control storage and subsequent execution.

The following is a description of IMPL. The nonvolatile storage device used is the 23FD Flexible Disk file. This file provides double-frequency data recorded on 32 concentric tracks of a flexible magnetic recording disk.

Each track contains 8 sectors consisting of a sync bit, a sector identifier (ID) byte, 256 bytes of data, and a check byte. The sectors are marked by photoelectrically detected sector pulses. A variety of commercially available low- cost low-performance disks or tapes could be substituted for the 23FD.

The IMPL process is divided into two parts. A small nucleus microprogram of 64 words (256...