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Browse Prior Art Database

Loadable Program Storage Feature for an Existing Fixed Program Device

IP.com Disclosure Number: IPCOM000042173D
Original Publication Date: 1984-Apr-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Day, MN: AUTHOR [+3]

Abstract

This article describes a hardware device (Function Extension Feature) enabling a previously fixed program device to be upgraded to a loadable program device by adding random-access memory (RAM) program storage that is accessible from the processor's instruction bus as well as the I/O bus as an I/O device. This allows the product to be extended without a major change of processors or hardware. The device has a processor in which the instruction storage and bus are completely separate from the data storage bus. The processor has no instructions capable of reading or modifying the instruction storage since the storage was meant to be read-only storage (ROS).

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Loadable Program Storage Feature for an Existing Fixed Program Device

This article describes a hardware device (Function Extension Feature) enabling a previously fixed program device to be upgraded to a loadable program device by adding random-access memory (RAM) program storage that is accessible from the processor's instruction bus as well as the I/O bus as an I/O device. This allows the product to be extended without a major change of processors or hardware. The device has a processor in which the instruction storage and bus are completely separate from the data storage bus. The processor has no instructions capable of reading or modifying the instruction storage since the storage was meant to be read-only storage (ROS). The loadable storage feature was developed to overcome this problem by adding RAM that is not only accessible by the Processor Instruction Fetch but also the processor's I/O bus as a standard I/O device. The attachment of the feature to the instruction bus allows the processor to fetch instructions from this storage as well as the fixed ROS storage. The connection of the feature to the I/O bus as an I/O device allows the storage to be read and written from the processor. In this manner the processor is capable of moving instruction data stored in data storage by a host system into the added RAM storage. The capability of the processor to read this storage serves two purposes. Since the processor is able to read from this storage, areas in this storage unused by the loaded program may be used as data storage. Secondly, the processor is capable of performing diagnostic checks on this storage by performing WRITE/READ/COMPARE tests using...